How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Anna Your Own Question
Anna, Pet Expert/Biologist
Category: Pet
Satisfied Customers: 11507
Experience:  40 yrs.: herps, pocket pets, rabbits, poultry, dogs, horses. Biology degree. Vet assistant.
Type Your Pet Question Here...
Anna is online now
A new question is answered every 9 seconds

I have a 90 litre fish tank it has a good filter and two air

Customer Question

Hello I have a 90 litre fish tank it has a good filter and two air pumps. In the tank I have two small comets and a medium sized wakin goldfish * I am a bit upset as I was told the wakin fish would be fine in the tank not realising at the time they are
related to a koi fish and should be in Ponds the pet shop said the two comets wil be fine too. I got told recently that the tank is too small the comets will out grow the tank and rehome the wakin * I love my fish they are very well cared for weekly water
changes good diet. What should I do? The wakin has been up in the corner latley but looks really healthy I can't afford a bugher tank at the moment. The ammonia is always o nitrite is always o nitrate is between 5-10.
Submitted: 1 year ago.
Category: Pet
Expert:  Anna replied 1 year ago.

Hello and welcome. My name is ***** ***** I'm a biologist with a special interest in fish. For now, your fish are fine. Your water parameters are excellent. Both the comets and the wakin are goldfish. They can all do well in either a tank or a pond. Your wakin is not a koi, and actually all goldfish are related to koi, but not the same species. The wakin looks quite healthy in the photo you sent. A fish may hide if the other fish in a tank chase it or harass it, so you may want to keep an eye out for such behavior.

So, it appears you were given some misinformation. What you do need to do though, is start saving for a bigger tank. Your fish will outgrow their present one, and you will not be able to maintain water quality when that happens.

It used to be recommended to have one gallon (about 4 liters) of water per inch of fish. That still holds true for tropical fish, but not for goldfish. There are various recommendations, ranging from 2 gallons (8 liters) per inch of fish to 30 gallons (about 113 liters) per fish, regardless of size. I’ll share my own experience with 12 inches total of goldfish (3 fish). They are in a 90 gallon (339 liters) tank. I have an undergravel filter, a hanging filter, and a powerful canister filter. It takes all three of those filters to maintain perfect water quality. Regardless of tank size, frequent water testing is always needed.

As long as ammonia and nitrites stay at zero, and nitrates below 40 ppm, your fish will be OK. When the numbers go up, it will be time to buy a bigger tank. If you have more questions, let me know in a REPLY. I hope your fish will thrive for a long time to come.


My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Please remember to rate my service only after you have all the information you need. Thank you!

Expert:  Anna replied 1 year ago.

Hello again. Do you need any additional information?