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Goldfish Care

Welcome to my general fish keeping page.
On this page you will find general information on keeping a goldfish health and happy.

Guidelines are recommendations by experienced goldfish keepers for those of lesser (or no) experience. They are not the only way of keeping goldfish, or even the best, but are our compromise between ideal conditions for goldfish and the space, time, and money limitations of the goldfish hobbyist. Koko’s guidelines are continually reviewed and updated as needed by the moderating team as we gain new information from research and experience.


Optimally, your tank should be large enough to provide at least 20 gallons for each goldfish, with a minimum of 15 gallons per fish. This is true for both long-bodied and fancy goldfish. While baby goldfish can do well in a smaller tank short term, they grow very fast, so we recommend starting them in their grown-up tank.

The ideal tank for goldfish is shallow with a large surface area. Tall tanks should be avoided if possible.


The most common filters for goldfish tanks are HOBs (hang on the back) or canisters. We recommend a HOB filter be rated by the manufacturer as turning over at least 10 times the tank volume per hour. Thus a HOB filter for a 20 gallon tank should turn over at least 200 gph. If one has multiple HOBs the turnover rates should add up to at least 10x the tank volume per hour.

Canisters have more filter volume, and we recommend they turn over at least 5-7 times the tank volume per hour.

There are many other types of filters, including many DIY filters. If you are using any of these, please start a thread in the Water Quality forum to ask if your particular filter is appropriate for your set up and your fish load.

Water Changes

We recommend a minimum of a 50% water change each week. This assumes that you are meeting the recommendations for tank size and filtration.


Aeration is not usually needed if your tank and filter(s) are large enough for your fish load, the water surface area is large enough to provide good gas exchange, and the fish are healthy. Even then, adding aeration is generally beneficial. We will often recommend adding aeration when treating sick fish.


Goldfish are called “cold water” fish, not because they require cold water, but because they do not require heated tanks like tropicals. Generally, healthy goldfish prefer the same temperatures as we do and are happy at room temperature (including a cooler night temperature). However, we may recommend heating the tank when treating sick fish, so it is useful to have a heater available.


Goldfish tanks may have no substrate, sand, or gravel. We recommend that hospital and quarantine tanks have no substrate for ease and completeness of cleaning. If one uses sand or gravel in the main tank, the layer should be no more than ½ inch thick. Gravel should be either small enough that the fish can easily swallow it or too large to fit in the fish's mouth.


Avoid hollow ornaments. The water in these can become anaerobic and produce toxins. Avoid ornaments that have sharp points or spaces that can trap a goldfish.


We do not recommend routine use of salt in a goldfish tank. Salt is a valuable, gentle medication which will lose some of its value if it is in the water on a regular basis.


We recommend quarantining all new fish for at least a month before introducing them to the “old” fish. During this quarantine period, we treat with salt and praziquantel.

Tank mates

Goldfish do best with other goldfish as their tank mates. Most other fish are likely to harm and/or be harmed by goldfish. Please ask about their suitability before adding any other kind of fish to your tank. Even fish that get on well in a goldfish tank, such as bristle nose or rubber lip plecos, or even large snails, produce waste. So adding these reduces the number of goldfish your tank can support.

Here are some articles with additional information about keeping goldfish.



Water Changes......

Amquel water
conditioner I have found over the years that changing 50%-60% of the water every week is very important, because of the large amount of waste they produce and the oxygen they use. When replacing the water you need to treat it with a detoxifier. I highly recommend either Prime or Amquel, it gets rid of toxins and also doesn't turn the chlorine to ammonia.


Frozen peas mmmmmm
Frozen Peas

There are many foods for the fancy goldfish. The best food I have found is Pro Gold<, the reasons for that is:

1. Flake food: The fish go to the top to gather the food which creates air in their swim bladder (which could cause swimming bladder disease (floating).
2. Pellets: There are two kinds, one is sinking which isn't to bad, but they have been known for mistaking rocks for the food.
3. Floating food and we run in to the same problem as the flakes.
Even though goldfish love to eat they really should only be feed once a day or once every two days. The reason is the food is digested very fast which means more waste in the tank and more clean up for you.
4. Gel food

If you have to feed them flake or any other pellet foods besides Pro Gold Please soak the food for at least one min. That way some of the food has absorbed some water and will not expand in the goldfish.

Goldfish love all types of food besides the ones that the pet stores carry:

Fresh foods: Romaine lettuce, Peas cooked, earthworms, eggs, cucumber, insect larvae, grapes,oranges, and spinach.

Dried Foods: Flake, Pellet, Tubiflex, Krill, Plankton, Brine shrimp, Blood Worms, Spirulina, and Daphnia


Nox Ick Ick
Nox, whatever There are a lot of diseases they can get, but the most common would be 'Ick' (small white spots). Ick is always in your tank but the fish only get it when they're stressed out or when tank conditions are poor. Ick is treatable and most of the time you can get rid of it quickly. I always have 'Ick Nox' on hand for emergencies. Salt may also be used to treat Ich. More info here Using Salt and On The Use Of Salt

The second most common is swim bladder disease caused from too much air in the food and high Nitrates in the water.

This can be a big problem if not caught in time. There are no medications for this. The best thing to do is not to feed for three days and then to feed just peas for three days (nothing but peas for three days!), reduce the amount of food you are giving to them and make sure that you soak their food if your using any other kind of pellet food or flake besides *ProGold.

If you need any more help with finding what you goldfish might have you should really go to Disease Diagnosis / Treatments.

A question about breeding......
How do you breed fancy goldfishes? How can you tell the differences between a male and a female? I have one oranda red-cap, a black moor, two orange colored one and one is speckled with black marks. Give me some advice!!!!!!!!!!!

The Reply

A very long cool period (*65 or so) followed by a gradual warming period triggers gold fish to breed, this is why they only breed once a year. A male will breed with any female, so they don't have pair bonds. Males will chase females during courtship, as their colors will intensify. It is only possible to sex adult fish during the spring breeding. Females will enlarge with eggs. Males will get white bumps on the head and gills. This is NOT Ick, but breeding tubercles.
More information on

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