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.
Your tank should be large enough to
provide at least 20 gallons (76 liters) for each goldfish. 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. If you provide less than 20
gallons per adult fish, you should increase the amount of water changed
to maintain water quality.
The ideal tank for goldfish is
shallow with a large surface area. Tall tanks should be avoided if
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 (76L) tank should turn over at least 200 gph (760
lph). 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.
We do not recommend internal filters for
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.
We recommend a minimum of a
50% water change each week. This assumes that you are meeting the
recommendations for tank size and filtration. If (for example) you have
one fish per 10 gallons (38L), you should do a minimum of two 50%
changes per week.
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, (a minimum
of 2 ft2 (1858 sq cm) per goldfish) 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
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..
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.