r/Goldfish • • Sep 19 '25

Discussions Goldfish General Master Care Guide

44 Upvotes

By: [u/IceColdTapWater](u/IceColdTapWater), Edited By: [u/TarantinosToes](u/TarantinosToes)

ENCLOSURE DIMENSIONS

For goldfish: 50-70 gal (200-280L) is required per adult common and 20-30 gal (80-120L) per adult fancy.

For koi: The general recommended minimum required is 250-300 gals (1,000-1,200L) and these are really better suited to large ponds.

Goldfish are indeterminate growers so while they do the most growing during the first 2 years of life, they never really stop growing so plan your tanks and stocking accordingly.

Ultimately water parameters (and fish behavior) will tell you if your tank dimensions, filtration, water change schedule is enough to manage the bioload produced by the number and size of the goldfish you have.

While smaller specimens may be okay on the lower end of the given volume range, larger specimens (10”/25cm+ for commons, 5”/12cm)+ for fancies roughly) may require even larger aquaria if not ponds. The bigger the better as bigger tanks are more stable in terms of water quality and parameters and will allow goldfish to grow to their full potential.

Fancy goldfish prefer horizontal over vertical swimming space, and some are bred to the point that their bodies are sensitive high water pressures (determined by the height of water). It is generally recommend to keep them in no more than 2’ (60cm) of water, especially for those with sensitive swim bladders. Common goldfish also appreciate horizontal swimming space so for this reason, avoid hexagonal and cylindrical tanks.

Some fancies, especially overbred ones and those that approach “show quality” conformations, may benefit from a heater set at a low setting (low-mid 70s °F (~ 21-24 °C)). The benefits of lower risks of constipation and bloat sometimes outweighs the negatives of a sped up metabolism.

FILTRATION

Generally, it’s recommended for a filter to cycle through 6-10x the given tank volume per hour depending on bioload. ALSO, take into account the amount of media a given filter holds, as media offers crucial surface area for beneficial bacteria to colonize.

If heavily stocked or feeding frequently a stronger filter (or the use of multiple in tandem) may be needed. Some filter options include: sponge, hang off the back (HOBs), internal, and canister (often holds the most media).

Some wrap the intake with a thin material to avoid fish from being sucked onto/into the filter. This may be necessary if dealing with goldfish fry, juveniles and sick/injured fish.

Filter media that is porous and has a large surface area (like Seachem Matrix and other similar products) is great for encouraging and maintaining large colonies of beneficial bacteria.

People will have opinions on which filter system is better, so focus on the amount of media the filter holds as well as gallons/litres per hour and find something within your budget which works for you.

Media should not be changed out unless it has degraded and is now irreparable/unusable or has been contaminated by toxic chemicals like cleaning products. To sterilise filter media, rinse with boiling hot water.

For new media, this should be introduced a week or two before removal of the old media to give the beneficial bacteria a chance to colonize the new surface area.

SUBSTRATE

Substrate offers enrichment for goldfish, as they enjoy rooting through the enclosure bottom for food scrapes. Bare bottom tanks mean they do not have that extra enrichment, however bare bottom tanks make for easier maintenance so are fine for QT/hospital tanks. If running bare bottom tanks for aesthetic or medical reasons, then adding large pebbles, free floating plants and plain terracotta pots can also work to provide goldfish with enrichment and shelter.

Pool sand is very popular, or plant-supporting substrate like fluval stratum. Pebbles run the risk of impaction unless they are much larger than the goldfish’s mouths will ever be. For sand, rinse thoroughly before use and avoid pH/hardness altering sands or live sand sold for cichlid and marine tanks.

PLANTS

FYI goldies are prone to plant destruction. Also, some plants grow best in substrate and others with their roots exposed. A full rounded fertilizer is highly encouraged to have, like Aquarium Co-op’s Easy Green or NilocG Aquatics’ All in One.

Anubias, amazon swords, lilies (toxic to nonfish pets like cats/dogs), water lettuce, java fern (and other ferns), bacopa, rotala, cryptocoryne, hornwort, anacharis, cardinalis, crinum, and moss are all options. There are many more. For anubias and cryptocoryne plants, do not bury the rhizome.

Pothos is an option but their leaves must stay out of the water to grow. It’s also toxic to nonfish pets (cats/dogs) but is okay in water with a pH ~ 6.5-9 as calcium oxalate isn’t really soluble in that range. People have used it for top cover and nitrate control. Shrimps love the roots. Bamboo is another option but must only be semi-submerged for proper growth and longevity.

Duckweed. A highly invasive plant. One duckweed plant can quickly lead to hundreds of more plants. A firm favourite with goldfish but be warned! Once added to your tank, it is very hard to remove.

Other floating plant options are: frogbit, salvinia, water sprite, water lettuce, water hyacinths and others.

CYCLING/PARAMETERS

Cycling refers to the nitrogen cycle and establishing a nitrogen cycle in your tank. The nitrogen cycle in aquariums is the process where beneficial bacteria convert toxic fish waste (ammonia) into nitrite, and then into less harmful nitrate. This cycle keeps the water safe and balanced for your fish.

For a tank to be considered cycled, the parameters must read 0ppm ammonia, 0ppm nitrites and measurable nitrates; ideally keep nitrates below 40-50ppm.

To keep parameters within acceptable ranges (0 ammonia and nitrite, 5-40ppm nitrates), water changes are needed. It is a good idea to siphon the tank bottom regularly to pick up excess waste and prevent parameter spikes. Make sure to treat the water with a dechlorinator and ensure the temperature difference is within 1-2 °C (1-5 °F).

If conducting a fish in cycle, you want ammonia and nitrite to be barely present as these are the most aquatic compounds; for ammonia the toxicity thresholds starts at 0.02-0.05ppm and ~ 0.05-0.15 for nitrites.

Higher levels of ammonia/nitrite may start negatively impacting your fish, including the risk of illness and death (via ammonia/nitrite poisoning).

During ‘fish in’ cycling, parameter spikes are likely and therefore water quality and fish behaviour needs to be monitored closely.

‘Fish out’ cycling means that you have to monitor parameters and do water changes to bring parameters to happy fish levels (0 ammonia and nitrite, 5-40 nitrates), but without the risk of stressing/harming fish. Fish food or ammonia solutions can be used to cycle your tank before the addition of fish.

However, in instances where the fish are already bought and in a severely undersized tank it may be better to do a ‘fish in’ cycle rather than wait for the larger tank to cycle completely.

A tank (without fish) is considered fully cycled once 2ppm of ammonia is converted to nitrates in about 24 hours. A cycled tank with fish will have no ammonia, no nitrites, and some nitrates. Even then, note that sudden increases in bioload can lead to cycle imbalances and parameter spikes. Be sure to syphon uneaten fish food, fish waste and slowly and gradually add new fish to your tank to avoid overloading your cycle and its beneficial bacteria.

It is highly encouraged to have a liquid test kit that tests for at least ammonia, nitrite, and nitrate like the API Freshwater Master Test Kit. Test strips are less accurate (especially dependent on manufacturer, expiration, and storage conditions) but are ok to gather baseline readings, especially in older and stable tanks.

Other reliable test kits include Salifert kits and NT Labs kits. Local fish stores may also be able to test your water, but it is advised that you get your own kit so that you can test you water whenever you need to and avoid LFS not performing or reading the test correctly.

ACCLIMATION

When you transfer goldfish from one enclosure to another, acclimation is typically necessary.

If the water source is the same and parameters are similar only temp/nitrate acclimation may be necessary. When the temp matches within ~ 2-5° F (1-2°C), parameter acclimation (if needed) can begin.

Gradually replace 20-30% portions of old water with the new enclosure’s water, waiting 5-15 minutes in between and carefully monitoring the fish.

These specific ranges are approximations, others methods or specifics may vary ie if drip acclimating. Also remember to try to transfer your old substrate and media when possible to help seed the process of cycle establishment.

It may be helpful to be extra vigilant of parameters during this time as well as fish behavior. Some stress may be expected at this time and the next few days, and some choose to do a light dose of aquarium salt to aid the process.

FOOD

Goldfish are omnivores, and quite frankly always hungry (they don’t have stomachs). Get a good sinking pellet as a staple food (protein roughly 40%), pre-soaked before being given to any hungry goldie. You can also feed frozen items such as: brine shrimp, blood worms, spirulina, plankton, fish, etc. You can also feed blanched veggies/greens such as spinach, zucchini, chard, etc. A good goldie diet is a balanced and varied diet.

Some goldies, especially fancies, are predisposed to swim bladder issues and constipation. Feeding soaked high quality and sinking food in small amounts but more frequently may help mitigate the risks of developing swim bladder problems. Repashy is an excellent balanced gel food that’s very easy on sensitive goldie stomachs. Hikari also make excellent sinking pellets.

MEDICATION

Medication will be more effective if given via feed rather than being introduced to the water column. If dosing in the water column, then make sure to remove UV, carbon media; smaller tanks can make it to easier to dose in the water column and ensure that the fish gets an effective dose of medication.

Medications often work by disrupting the growth cycles of organisms and their metabolic processes. That being said, do not give one medication via multiple ways at once and be very careful when mixing medications. This is best avoided, unless using safe medication combinations or following vet recommendation.

Be very mindful of dosage, and consider partial doses if your fish is very small or more weakly dispositioned. Note that some chemicals, like salts, are only removed via water changes are may adversely affect plants and scaless fish such as catfish and plecos. Weakened fish may not tolerate medication as well to be very careful; use half doses if necessary.

Also note that certain medication can impact water parameters or tank cycle stability. Oxygen levels can also be adversely impacted which is why it’s recommended to have extra surface agitation (add spray bars, air stones).

Raising the temperature of the water may help to disrupt certain infectious organisms’ life cycles as well as to provide a metabolism boost, but always ensure adequate oxygenation when using meds at the same as increasing the temperature.

FYI: API products with the suffix ‘-fix’ mainly use natural oils instead of manufactured medication and are less effective than said manufactured medications. Also avoid any algae-fix products, these can deplete oxygen levels and kill fish.

Antibiotics: Be careful when using antibiotics especially. Not only can these impact your beneficial bacteria, but they can also be rough on fish (i.e. kidneys etc) so only use if necessary to treat nasty injuries and infections.

Do not dose pre-emptively as a prophylactic measure. Note that getting antibiotics in certain countries is illegal without a veterinary prescription, so follow your local laws. Be careful when obtaining medications from abroad via third-party sellers.

GENDER

Breeding tubercules on the gill plates/anterior portion of the pectoral fins, vent shape, and gamete expression (the only sure way) are the main ways to tell gender. As always there are spectrums for any particular phenotype and any one goldfish may not always fit a certain physical description.

When females are gravid, the males may harass them, especially by nudging their vents. Gentle egg expression and avoiding temperature fluctuations may help. You may need to separate if the female becomes stressed.

TANK MATES

A general consensus is to try to keep commons with commons and fancies with fancies (especially the slower swimming ones or ones with protruding eyes). Keeping them together runs the risk of the commons outcompeting or bullying the fancies, but cohabitation does successfully occur.

However, some keys points of success to consider are ample space, filtration, plants/wood/decor to block lines of sight, and enrichment. Ensure that aquarium décor is free of sharp edges and small holes. Goldfish are clumsy and curious and will get themselves trapped/injured looking for food.

You should be ready to temporarily/permanently separate individuals if necessary.

Commons and koi can potentially be kept together, given that the commons are of adequate size of about 6” (15cm). Some ryukins/fantails may also be possible, given that they’re also long enough and of a slimmer body conformation to keep up with the commons and the koi.

Here is a by no means comprehensive list of other potential/discouraged cohabitants. As with any situation, monitor fish behavior and make sure ideal parameter ranges are comparable.

Potential – Can usually coexist but caution is advised

White Cloud Mountain Minnows: Possible, but the goldfish may eat the minnows if they’re small enough and the minnows may fin nip.

Danios: Possible, but the same risk as the white cloud minnows.

Shrimp: Possible, but may become goldfish snacks depending on size and individual fish’s’ temperaments.

Snails: Possible, but goldfish may harass/eat them. It depends on the size of the snail and the individual fish’s temperament.

Dojo Loaches: May potentially bully goldfish, but the pairing may work in larger setups with lots of plants and décor (loaches love tunnels and caves). They will go after certain snails as well.

Mollies: Some species can tolerate lower temperatures than others. They may fin nip, and goldfish may try to eat them if they can fit in their mouths.

Platies: Some species can tolerate lower temperatures than others. Platys may nip at goldfish fins, and goldfish may try to eat them.

Discouraged

Hillstream Loaches: These fish require massive water flow and oxygenation that goldfish do not like and may find stressful.

Corys: Goldfish can choke on them, especially because of their defensive barbs. Some species have venomous barbs that can harm your goldfish as well. If a goldfish swallows a cory, the barbs can get lodged and make extraction very difficult.

Bettas: Bettas can be territorial and may try to “defend” their territory. Large enough goldfish might eat them if possible. Undue stress for both parties may occur, plus bettas are tropical fish.

Cichlids: Cichlids are subtropical/tropical, aggressive fish.

Barbs: Their temperature ranges only slightly overlap, and most are aggressive in nature and will fin nip.

Plecos/panaques: Some, like common plecos get absolutely ginormous and most prefer tropical temperatures and soft/acidic water. Even smaller types like bristle nose plecos can injure goldfish by latching on to them to feed off their slime coat.

Turtles: Many turtles will happily take chunks out of goldfish when given the opportunity. Goldfish, as prey animals, will also experience stress being homed with a predator.

Axolotls: Axolotls may accidentally nip at or consume goldfish, which is good for neither of their health. Goldfish are super waste producers and axolotls are particularly sensitive to parameters.

Frogs: Same risk of predation as turtles/axolotls. Parameter requirements may also differ depending on species.

Crawfish: Same risk of predation as turtles/axolotls/frogs. They are opportunistic predators and may happily feed on goldfish (especially if hungry).

FAQ/COMMON DISEASES

Q: Is my goldfish pregnant?

A: Goldfish do not carry live young, but females do develop eggs and then release them to be fertilized. Although this can make the female appear a bit engorged and swollen, check that she’s not egg-bound, constipated, or has dropsy (pineconing of the scales often also occurs in tandem). Manual expression is an option but should be researched and done with caution.

Q: Why is my goldfish changing colors?

A: Goldfish color is unstable, especially in their first 1-3 years of life when their growth rate is typically the highest. Fry typically start out very dark/bronzy, but usually develop colors due to their chromatophores developing after a few months of growth.

Black is especially prone to change. Note that the sudden appearance of blackened skin and scales can be a sign of a water quality issue, so check water parameters. If parameters are ok, then it is likely a natural color change so no treatment is needed.

Certain foods such as spirulina contain carotenoids, which are pigments that enhance goldfish color. Some carotenoids are also converted into astaxanthin which contributes to reddish coloration. Note that even a carotenoid heavy diet will not magically change a goldfish’s coloration, as genetics are the main factor.

Q: How to transport fish?

A: The most common way is a lidded bucket/container filled with tank water. A bubbler is suggested, especially for longer transports. Also account for the time to disassemble and reassemble your enclosure. Make sure to keep your substrate and filter media moist to seed the cycle in your new place.

Another way, for shorter trips, is a simple but very secure bag (I double bag) with enough water for the fish to be comfortably submerged but also with enough air for oxygen to diffuse. Sometimes people use methylene blue during transport to try to reduce stress. After moving, your fish may be stressed for a few days and may benefit from a few days of fasting, reduced feeds and reduced light.

Q: Aquarium salt vs epsom salt?

A: Aquarium salt (NaCl) is excellent for external issues/injuries, as well as stimulation of the slime coat and increased osmoregulation. It’s a good all rounder as an antibiotic/fungal/parasitic. Epsom salt (MgSO4) is excellent for internal issues such as constipation and fluid retention.

Epsom Salt Dosage: 1 tsp/5 gals (20L)(tank), 1 tbsp/gal (4L)(bath).

Aquarium Salt Dosage: 1tbsp/5 gals (20L)(tank), 1 tbsp/gal (4L)(bath).

Invertebrates, plants, and certain goldfish are sensitive to salinity. As with any treatment, monitor fish behavior. It may be good to have two baths of a salinity gradient to help lessen the transition to and from, and to change out salt in the tank slowly. Salt, like other treatments, may impact with oxygenation and a bubbler may be helpful.

Q: What is methylene blue and can I use other dyes?

A: Methylthioninium chloride is cationic dye used in the aquarium hobby as an antifungal/parasitic/bacterial. It is also helpful for ammonia and nitrite poisoning, but can crash your cycle, harm plants above 4mg/L (quart) and dye decor (which is often why it’s used as dips, dabs, or in hospital tanks). Dosages will differ depending on usage and percentage.

Methylene Blue Dosage (2.5%): 1tsp/10 gals (40L)(tank), 5 tsp/3 gals (12L)(bath)

You can use other dyes. Some others used include: malachite green, potassium permanganate, or gentian violet. Check dosages carefully.

Q: How to choose antibiotics?

A: Unless you know the specific bacterial infection, it’s best at first to a broad spectrum antibiotic (kanamycin, sulfathiazole, nitrofurazone). An aquatic vet (or very experienced keeper) can do a skin scrape/fecal test.

Gram positive antibiotics include: erythromycin, amoxicillin, and penicillin.

Gram negative antibiotics include: minocycline, tetracycline, kanamycin and oxytetracycline.

Both: metronidazole, sulfa meds, mitrofurazone

Note, medication can impact oxygenation and water quality so monitor parameters and fish behavior closely.

Q: Antifungals?

A: Dyes (methylene blue, malachite green, potassium permanganate, gentian violet) and aquarium salt are options via the water column. Note dyes will indiscriminately kill your beneficial bacteria too and are best given as baths or in hospital tanks

Metronidazole and copper sulfate are options you can give via feed or the water column. Note, medication can impact with oxygenation and water quality so monitor parameters and fish behavior closely.

Beware! Do not use aquarium conditioners and other reducing agents like Seachem Prime if using copper based products! Toxic copper compounds will cause harm if they are combined. Remove invertebrates like snails and shrimp as well.

Q: Antiparasitics?

A: Aquarium salt, praziquantel, copper sulfate, formalin, and metronizadole are options you can give via feed or the water column. Note, medication can impact with oxygenation and water quality so monitor parameters and fish behavior closely.

Q Why did my goldfish die?

A: There are many factors.

Where you got the goldfish and where the seller got them matters. If they were raised in horrendous conditions you may get stunted, diseased fish. Big box pet stores like Petsmart, Petco, and Pet Supplies Plus are notorious for their bad husbandry and their questionable animal breeders.

The tank must be properly cycled and able to handle the given bioload. An incompletely cycled tank or too big of a bioload increase can result in parameter spikes. It’s advised to add fish slowly, and to monitor water parameters via a liquid test kit.

The fish must also be properly acclimated. If two enclosures’ water parameters vary too wildly and the goldfish is added in too quickly they could go into shock. Temperature must also closely match to avoid undue stress.

Disease is very prevalent among fish, especially chain store fish or fish from improper breeders. Inflamed skin, stringy white poops, missing scales, torn fins, bulging eyes, grayed skin are all signs of disease or parasites although there are much more.

When making a sick fish post, try to include as much detail as you can along with helpful pictures and videos. Listing water parameters in numbers helps a ton.

Q: What is ammonia burn?

A: Ammonia burn is a chemical burn. Technically you want no ammonia, no nitrite, and 5-40ppm of nitrate. However, fish in cycling sometimes includes parameter spikes and the temporary “acceptable” levels of ammonia and nitrite are between 0.05-0.15ppm. To treat, water changes is the most important. Aquarium salt is also a common treatment. Fish exposed to ammonia can also benefit from being given a methylene blue bath which can chemically reverse the effects of ammonia poisoning.

Q: What is dropsy?

A: Dropsy is fluid retention and is a symptom of organ failure rather than a disease in it of itself. Usually the resulting damage’s effects are chronic and will eventually result in the death of the fish, especially if caught in later stages (with pineconing).

Epsom salt is used to attempt to regulate fluids, along with a broad spectrum antibiotic in attempt to tackle infection. Ultimately dropsy is fatal, barring rare exceptions. If successfully treated, then view dropsy as a chronic condition the fish is in remission from but relapses are sadly very common.

Q: What is septicemia (red pest disease)?

A: A typically gram negative, contagious bacterial infection that causes hemorrhaging, red blotches on the body, and streaks of red in the fins. Septicemia can occur in tandem with ammonia poisoning as water quality is a common cause. Can also be confused with the effects of ammonia stress/poisoning as well as other conditions like flukes or bacterial epistylis.

Treatment typically involves dyes or aquarium salt, along with an antibiotic feed. Note that septicemia is quite rare and viral and infectious septicemia even rarer in private/small aquaria. Do not panic if you see red streaks or blotches on your fish. It’s probably not septicemia.

Q: What are these white spots?

A: Many potential causes.

Ich: Ichthyophthirius multifiliis, a contagious protozoan parasite. White, uniform and shape and flat to the skin, appears on both the body and the fins but not on usually the eyes.

Treatment usually includes aquarium salt or dyes, an antiparasitic med/feed, antibacterial/antimicrobial/antiseptic med and raising the water temperature to speed up ich’s lifecycle. If increasing the temperature, be sure to ensure plenty of oxygenation.

Epistylis: Epistylis is a genus of contagious, ciliated protozoan parasites. Can be grey to whitish in color, sticks out into the water, varies in sizes with patchy coverage and can also occur on the eyes. It can be fatal if left untreated and is a lot more aggressive than ich.

Treatment is the same as ich (aquarium salt or dye, an antiparasitic feed/med, antibacterial med/feed but avoid raising the water temperature).

Head and Lateral Line Erosion (Hole in the Head): HitH is caused by a mix of factors including stress, poor water quality, poor filtration, and an unbalanced diet. Potentially linked to Hexamita protozoans, potentially infectious. Mainly affects cichlids and rarer in goldfish.

Symptoms can manifest as inflamed/protruding lateral lines, as well as white lesions on the head that eventually can become deeply pitted and essentially erode the flesh. Open wounds can lead to secondary infections that in combination can be deadly.

Treatment includes fixing water quality, aquarium salt or dyes, medicated feed for secondary infections, and providing a more balanced and varied diet.

Carp Pox: Fish herpes HPV-1. Caused by a virus, symptoms can manifest as white dots to waxy white/pink/gray growths on the skin or small “blisters” on the tail as well as on the mouth. Infectious, and can come and go. More unsightly than harmful.

Treatment includes treating any open lesions with aquarium salt or dyes dips, treating any secondary infections, raising the temperature, and keeping the water clean.

Lymphocystis: A contagious viral infection caused by the Iridoviridae family. Commonly known as “cauliflower disease” due to the pinkish/whitish growths that look like little piles of curd.

Since it is viral in origin, no commercial antifungal or anti-bacterial treatments exist that specifically target it. However, treatments includes treating any open lesions with aquarium salt or dyes dips, treating any secondary infections, raising the temperature, and keeping the water clean. Vets can excise large, bothersome lumps.

Cotton Wool Disease (Saprolegnia): A “fungus” (actually a water mold) that usually presents as groups of fuzzy white filaments that stick out from the body.

Treatment includes an antifungal med, dyes, aquarium salt, and raising the temperature.

Anchor Worms: Anchor worms are parasites that present as whitish/brownish dots to full on whitish strings protruding from the body/fins of the fish. The place of connection is often red and inflamed.

Treatment usually includes aquarium salt or dyes, an antiparasitic feed, and raising water temperatures.

Q: What is this lump?

A: Multiple potential causes.

Tumor: Tumors contain cells that are multiplying out of control or fail to die. They can be either benign or malignant (cancerous and can spread). Treatment includes treating an open lesions and removing bothersome tumors, especially ones blocking gill and mouth function. For tumor removal, seek veterinary advice!

Cyst/Abscess: A fluid filled sack. Can sometimes be caused by bacterial infections. Treatment includes draining, antibiotic feed, epsom salt, and the treatment of open lesions.

Q: What is fish lice?

A: Parasitic crustaceans. Treatment involves aquarium salt and an antiparasitic feed. Methylene blue baths may also be beneficial. Severe infestations may require the cleaning of substrate/decor (even though this impacts the tank cycle).

Q: What is popeye?

A: Popeye can have many causes (commonly caused by the gram positive corynebacterium but also viruses, poor environmental conditions, etc). Symptoms include bulging eyes/sclera and potential eye bursting.

Treatment includes antibacterial feed, epsom salt, and the potential treatment of a popped/missing eye. If one eye is popping out, it is usually a result of trauma and will resolve by itself. If both eyes are popping out, there is likely an underlying infection at play (look for pineconing and signs of dropsy) and will require antibiotics.

Q: What is the swim bladder, and what is swim bladder disorder?

A: The swim bladder is a gas filled expandable sack in fish used to control buoyancy and swimming patterns. Disorders of the swim bladder can lead to buoyancy issues and potential bloating/constipation.

Epsom salt via a bath or tank addition is one of the typical steps for buoyancy issues, though dosage depends on whether the salt is to be a dip or a tank exposure (invertebrates and plants can be sensitive to salinity).

This is usually in tandem with a couple days of fasting, followed by small easily digestible meals such as Repashy or shelled peas. If no signs of improvement show in about a week or two, it may be a congenital issue or due to another factor eg trauma, fluid build up. At this point veterinary care may provide additional answers/treatment options (x-rays, swim bladder aspiration).

Q: What are flukes?

A: Flukes are contagious microscopic flatworms that can be both on the gills and the skin. Symptoms include flashing (twitching/itching), small red dots, red splotches, fin fraying, bottom sitting, laboured/fast breathing, and spitting food out.

Treatment usually includes aquarium salt or dyes, an antiparasitic feed/med (praziquantel works best). Since flukes can lodge in the gills and gill function and oxygen uptake, provide plenty of oxygenation and avoid increasing the temperature.

Q: What is Costia?

A: A single celled parasite, costia multiplies particularly quickly in cooler water temperatures. They will dig through the slime coat and attach to the skin/gills.

Treatment includes aquarium salt, elevated temperatures, and medicated antiparasitic feed. Methylene blue baths may also help.

*Q: What is Velvet Disease ?*

A: Velvet disease is caused by a parasite that manifests as small *gold/rust*-colored spots. Its three life stages are very similar to ich in which they have phases where they live freely in the column and attached to a fish.

Treatment includes aquarium salt, a medicated antiparasitic feed, and methylene blue applications. Do not raise the tank temperature. A UV filter may help kill the free floating form of velvet.

Q: What is Camallanus?

A: Camallanus are contagious flatworms that infect the digestive tract and can sometimes hang out of the fish’s vent as red threads. Symptoms also include bloating, white poop, and lethargy.

Treatment usually includes aquarium salt or dyes, antiparasitic feed/med, and raising water temperatures.

Q: Deformed gill plate?

A: Deformed gill plates are due to congenital malformations. Goldfish with deformed gill plates can live healthy long lives given extra precautions are taken for the exposed gills.

Q: White/clear/floating poop?

A: Sometimes fish occasionally pass opaque poops or poops with trapped gas in them. If only passed occasionally it can be normal. However, a lot of poop of that description can be a sign of internal parasites or infection.

Treatment could be antiparasitic feed/med, epsom salt, or smaller meals (soaking dry food beforehand). Blanched veggies are also easier on their stomachs.


r/Goldfish • • Aug 08 '25

Discussions Introducing a new flair: Beginner Help (If you are new to fish keeping, use this flair!)

32 Upvotes

Hi everyone!

After getting feedback about how some new users sometimes feel like they are treated harshly by other more experienced users, I've decided to introduce the Beginner Help flair.

What does this flair mean?

If you see a post with the Beginner Help flair, it’s your signal that:

  • The OP is new to fish keeping and needs extra patience and guidance.
  • The goal is constructive + supportive help! No nitpicking, sarcasm, elitism.
  • If you can’t give advice without being respectful or are simply tired of new fish keepers, just skip these posts.

Think of it like a new driver/ L sticker on a car - maybe these beginner fish keepers are young people and minors living with relatives just trying to do their best for their pet, maybe it's someone whose child won a fish at carnival, or someone who got misled by their LFS. Yes, it might also mean someone who didn't do enough research but the fact that they're asking for help is the most important step. On my end it will mean focusing moderation on these beginner posts as well just to ensure people are getting help and not being dogpiled upon.

Do I need the Beginner Help Flair?

Now I'm certainly not one to gate keep this hobby so I won't impose a definition, but I would suggest users use the Beginner Help flair if your post falls under the following:

  • First goldfish tank or pond (or first time keeping goldfish in many years)
  • First time with fancy/common goldfish varieties
  • Learning about tank cycling and water quality requirements specific to goldfish
  • Basic setup questions including tank size, filtration, aeration, substrate
  • Addressing beginner mistakes like overcrowding, small tanks, or mixing incompatible species

For diagnosing diseases, please still use the Sick Fish Help flair.

Hopefully this goes towards addressing some of the problems here and do let me know if the new flair isn't working. Thank you!


r/Goldfish • • 6h ago

Full Tank Shot Today v 2 years ago

24 Upvotes

225g community tank with 3 goldfish, 3 golden dojo loaches, 10+ variatus platy, & a few hitchhiker snails.

Adding a pic in the comments of one of their previous tanks(2 years ago today). The goldfish moved between a 29 tall, 29 long, 40g, & 65g before finally settling in here a few months back.

If anyone has hardy plant/additional cohabitant suggestions I'm open to all ideas. Thanks for looking!


r/Goldfish • • 5h ago

Full Tank Shot Two Ranchus in a 20 gal long grow out tank. They seem happy. First time properly keeping goldfish after researching

Post image
5 Upvotes

Waiting to see how they do with the current plants, if they don’t eat them, I’ll add more. Has a 50gallon and a 10 gallon sponge filter hiding behind the plants


r/Goldfish • • 19h ago

Fish Pics Shogun goldfish

48 Upvotes

Shogun goldfish super beauty


r/Goldfish • • 3h ago

Tank Help best vacuum for sand?

1 Upvotes

i have a 75 gal goldfish tank and recently changed to white sand substrate. i know the white sand will get dirty quickly with goldfish but the current siphon vacuum i have is not doing the best job to clean the debris and poop. it is a taller tank and all the vacuums im looking at have pretty mixed reviews. leaning towards an electric vacuum but wondering if anyone here has sand and has a good recommendation for a vacuum?


r/Goldfish • • 3h ago

Questions Multiple Questions From First Time Goldfish Owner (LONG)

1 Upvotes

Hi all,

On September 19 I won a pair of juvenile goldfish at a carnival. A month later they're in what I currently consider their final setup. But as someone who's never cared for any types of fish, I'd love any advice—unsolicited or not—on how to properly care for them and maximize their health and lifespan.

I won them to make my almost-4 year old daughter happy having no idea the amount of work that was coming my way. 😄

I'll share this as a timeline of events partnered with a series of questions. Kindly let me know what I should have done differently or what I should be doing differently moving forward.

I'm going to be asking A LOT of questions and sharing A LOT of pictures. Feel free to cherry pick things you know the answers to and ignore the things you don't, or feel free to answer every question in detail.

I'm doing this so I can be thorough and use this thread as a one-stop shop for all the information I'll need to take care of these little guys for the rest of their lives.

For starters. Here they are today:

Do they appear healthy? Is there anything in their appearance or behavior that would concern you?

https://reddit.com/link/1xavk2p/video/s49a3fbp0nwh1/player

On September 19 they were acquired in the following tiny tank:

They were in this tank for 3-4 days before I was able to acquire a 2.5 gallon tank. They were in the 2.5 gallon tank (pictured below) for about 2.5 weeks. So the 2 fish were in just 2.5 gallons or less for about 3 weeks. This excludes any time they spent in cramped quarters prior to my acquiring them. I have no idea what their conditions were prior to me winning them.

During their time in this 2.5 gallon tank, I was caring for them as follows:

1. Daily morning feedings with the flakes that came in a Ziplock with the fish.

2. Daily changes of 2/3s of the water.

3. Daily water conditioning.

4. Water temperatures maintained as consistent as possible.

After 3 weeks, they were transitioned to a 75 gallon tank I acquired on Facebook Marketplace. I cleaned it with water and white vinegar. I filled it with water temperature at about 64 degrees Fahrenheit. The water was conditioned as instructed. I changed the bottom from gravel to sand as I read they like to pick at the gravel and it could injure their gills.

Since this time, I've been doing the following. As this is the current state of the operation, I have the following questions for you.

1. I have about 4 inches of space at the top of the tank. This is to prevent them from jumping out before it doesn't have a lid. At their juvenile size, is this sufficient for now?

2. The tank apparently was a custom tank, so unfortunately there are no lids that are made for this tank. There's no center bar to balance plexiglass or Lexan and prevent sagging. At this point, I'm leaning towards simply getting three aluminum panels of 16x20 inches at 1/16th an inch thickness. That's lightweight, would cover the whole tank, and wouldn't sag. There's about 1.25 inches on the sides to support the panels (so 2.5 inches total). I read that's plenty.

Is this a terrible idea? I can't come up with anything better save for building a custom lid, something that I just don't have the time or acumen for at the moment.

3. Is a lid 100% necessary with goldfish long term? Do common/comet fish jump out if the water i cared for properly?

4. I'm currently giving them water changes every 5 days. I'm changing out about 60% of the water. I have the tiny filter from their 2.5 gallon tank still working here to circulate any beneficial bacteria that formed. I condition the water as instructed by the bottle. I also have a new filter (will get to that in a moment). I do my best to match the temperature to the old water.

After a month, I would love it if I could do more infrequent changes. What would you recommend?

5. Is this a suitable set up for the rest of their lives? Is 75 gallons enough for 2 adult goldfish?

6. How big do you expect them to grow providing I do give them proper care?

7. Can I add additional fish that create less waste than goldfish do, or is this the maximum amount of fish I can have for gold fish to thrive?

8. I bought them the following tank stand. It claims it supports 1000 pounds. All in, I assume my tank, water, stuff on the shelves, the sand, and all the accessories probably lands me at about 900 pounds. Maybe a little less. So my question is, if a tank stand on Amazon is claiming 1000 pounds, is that reliable? It seems fine today, but I need it to be fine 10 years from now. Here's what I bought:

8. You'll notice the lights atop the tank. They are submersible LED lights (pictured below). I currently have them dragged cross the top of the water with old phone chargers (unplugged of course!) It's just functioning as "string". I can't imagine this isn't safe but do you have any reservations providing the cords are confidently secured?

9. Here is their water filter. Is it sufficient, and how often do I need to clean it/change it?

10, Here's their food. I'm currently giving them 6 pellets each in the morning, and then again in the evening. Two Part Question: Is that enough/too much? Also the one with the black fin tips is kind of a bully and really seems to eat almost all of it no matter what I do. The purely gold one tends to only get the scraps on the ground.

To be honest, I'm not even sure if it's a problem. The purely-gold one will often swim directly by a falling pellet and ignore it. She seems to prefer foraging it from the sand. The other one waits at the top of the water for every possible pellet when she sees me coming.

11. Last but not least, I use the following strips to test for all the things you need to test for. Ammonia, Nitrates, etc. Right now I'm doing it every 2-3 days. Is this sufficient. Long term, do I even need to bother if I'm regularly changing the water?

Also, is the levels it reports on (especially for Ammonia) granular enough. If I go from 0.0 to 0.5, did I need to know if it was at 0.2? Or is what you see below a granular enough indication for me?

THANK YOU!!! Please feel free to comment on any of my questions or provide any additional insights!


r/Goldfish • • 5h ago

Sick Fish Help Injured scale NSFW

Thumbnail gallery
1 Upvotes

r/Goldfish • • 1d ago

Fish Pics 15th july '26, 15th oct '26

Thumbnail
gallery
70 Upvotes

r/Goldfish • • 6h ago

Beginner Help What type of goldfish should I get?

1 Upvotes

I'd like to keep 1-2 indoors. I have planted breeder to start with, but will upgrade as they grow.

I know some goldfish are more prone to diseases than others. I'm looking for a hardy breed. All tips are welcome!


r/Goldfish • • 9h ago

Discussions Behavior/healing

1 Upvotes

Hi all. For the longest time i had a mopani arch in my tank with my moor, theres never been any issue with it until yesterday all of a sudden she decided she wanted to dig herself under it intensely looking for food and ended up with a gash on the gill and her side. I did take the wood out and treated the tank with some melafix. I just feel horrible and wonder if theres anything more I can do. (i did recently just rescue a ryukin and regrew its tail fins so ill be approaching it with the same things I just feel terrible)


r/Goldfish • • 11h ago

Pond Please me set up my outdoor pond!

1 Upvotes

Hi! I have 2 common goldfish and am trying to set up an outdoor plastic stock tank.

I got these fish from someone who won them at a fair and now am trying to be a good pet owner but also am balling on a BUDGET.

Found this 100 gallon tank

This 400 GPH water pump

And this metal mesh cover to protect from animals

I need to figure out the rest of the filter but am sort of lost and already these few items set me back like $350 … I’ll get more rocks for the bottom and have air stones and tank decor that can be transferred from their current setup. Eventually I think it would be cool to set up an aquaponics system but for now I just need the basics… please help! I’m not a fish person and am so confused, the fishies are healthy and happy now in their tank, but I want them to have a better set up and I’m worried they’re going to outgrow their current home soon because they are already so much bigger than when I got them.

Any help is GREATLY appreciated. I wanted this to be fun but have been a bit overwhelmed by the project as I don’t have a large outdoor space, budget, or experience here. Thank you!


r/Goldfish • • 11h ago

Sick Fish Help Found this in the fin of my oranda! And the oranda isn’t moving and is laying sideways most of the time and upside down. What should i do? NSFW

1 Upvotes

r/Goldfish • • 1d ago

Questions “Lists forward”??

Thumbnail
gallery
10 Upvotes

I am looking at this fish on Zhao’s website and it says that he “lists forward”. I’m assuming this is referring to that his head tends to be lower than the rest of his body. Is this okay? I don’t mind if he is a little “different” but I don’t want this to be harmful to him in anyway. I’d rather know before I buy.


r/Goldfish • • 16h ago

Questions Injured scale

Thumbnail gallery
2 Upvotes

r/Goldfish • • 17h ago

Sick Fish Help Please help NSFW

2 Upvotes

Anyone know what this is on the side of my goldfish? I just noticed it today and she didn’t have it before. I did recently swap out their tank and added some driftwood, but my driftwood is pretty smooth although it does have some height. I’m wondering if she could’ve injured a scale on the wood?


r/Goldfish • • 16h ago

Sick Fish Help Shubunkin goldfish has very red gill on one side? NSFW

Thumbnail gallery
1 Upvotes

I've had him about 2 months and I brought him in from the pond this week. I worry the parameters were bad out there, and that somehow caused this. I don't know if he's had this very long. I think the white spots are breeding marks but I have no clue about the red gill. He is full of energy and is not acting sick at all. Thank you!!


r/Goldfish • • 2d ago

Arts and Crafts Little goldie sticker I made today ◝(ᵔ-ᵔ)◜

Post image
187 Upvotes

r/Goldfish • • 1d ago

Sick Fish Help White spots getting worse NSFW

2 Upvotes

Please tell when what you guys think it is? I cant tell for sure. Ive never kept fish before him and no photos online are helping me identify. They almost look raised?


r/Goldfish • • 23h ago

Fish Pics What kind of goldfish are these two? The smaller one follows the bigger one around everywhere! I think they are siblings but Petco told me they were different kinds.

Thumbnail
imgur.com
0 Upvotes

r/Goldfish • • 23h ago

Beginner Help Goldfish Aquarium Size

1 Upvotes

Hi! I’m going to be setting up a goldfish aquarium here soon and I’m wondering if I should go with a 40 gallon or 60 gallon. I only want two fancies, I’m thinking Oranda.


r/Goldfish • • 1d ago

Rehoming pond comets need new home...just south of boston

2 Upvotes

So I am at the edge of overstock, and yet no matter how much I tell them to knock it off, they had more babies. I could have, should have, would have left them to attrition but .....well to be honest I wanted to see what I got for color. So now I am sitting on 2 to 3 dozen babies (1 to 2 inches long) that need to be relocated before the above ground IBC tote can no longer house them due to freezing temps. I am willing to let some of the larger fish go as well (4 plus inches)......and no I went bigger with the pond last year, not due for enlargement until 2029.


r/Goldfish • • 1d ago

Chonker The chunkiest goldfish! Meet Leonardo!

Post image
25 Upvotes

r/Goldfish • • 1d ago

Sick Fish Help Not sure if swim bladder issue or organ failure - please help NSFW

Thumbnail gallery
2 Upvotes

This is 14 year-old Koji. He's very poorly and I don't know if there is still hope or if it's time to let him go. I'm very emotional about this so please be kind.

He's been like this for 2.5 days. On the day I started treatment, I removed the gravel substrate to prevent injury to the side he is laying on. The tank is a 200 litre tank and he's the only inhabitant. It has a Fluval 307 external filter.

I have completed a 50% water change and the parameters were great after that. Unfortunately I didn't get a photo of the test strips before starting the Swimbladder Treatment from NTLabs. This is why the tank water is such a neon yellow colour.

I handfed a couple of blanched peas and they have passed through. That was on Saturday (17th) and he has been fasting since. I've spotted him trying to move around a few times but he cannot get to the top of the tank and can't even remain upright for more than a second or so.

There are no vets in my area that will provide treatment for fish - we've been calling them all this morning. He's a very old boy and I understand it might be time, but there's a tiny part of me that's hoping for recovery. Does anyone have any advice? I can provide more photos of the tank if helpful.


r/Goldfish • • 1d ago

Tank Help Is this Fish tank size good enough for goldfish?

Post image
14 Upvotes

Is this tank big enough for 4 goldfish?