How many goldfish can I put in a 32-liter tank without overcrowding?

Thanks for reaching out about Timothy and Lola. First suggestion is to get a large tank. The general rule of thumb is 1" of fish per 3 gallons of water. Test and correct water quality for pH, ammonia, nitrites and nitrates. The better the filtration, the higher the bio-load. So better filtration or a second filter could help. Good luck.

Hi, and thanks for your question. There is a general rule about it which is a rough estimate not to overcrowd your aquarium and avoid excessive production of feces and organic debris. The rule is one Inch per gallon, so in 10 gallons there should be ideally 10 inches of fishes in total. You should consider as well the presence of plants and gravel and any other sort of things, which decrease the water volume of 5-10% (so 10 liters are actually 9-9.5). This rule does not consider modern filtration systems. These fish suffer genetically from a certain grade of visual impairment, so overcrowding (especially competition for food) is not recommended. At the same time, please consider as well that schooling fish (like they are) should be kept in numbers, which means more space will be needed, so be generous.

The goldfish can get very big and may require a significantly larger tank as they grow and grow. As a rule of thumb, you need 1 gallon of water per inch of body length of fish. So if you have three 1 inch fish, you will need 3 gallons of water. I suspect you are at your max already in the smaller tank. Just so you know, most people do not have goldfish in tanks with tropical fish. You may consider getting two tanks One for your cold water fish like the goldfish, and one for your tropical fish that require a warm water temperature. For the goldfish I would suggest a minimum of a 20 gallon tank. For the Danio, I suggest to get a few more of these as they are schooling fish and a 10 gallon would be just fine. I hope this is helpful and please feel free to post any additional questions.

Adding more fish would likely cause overcrowding. This, in turn, could lead to stress, illness and aggression. You are probably at or very close to maximum capacity, especially if you have fish that are still growing.

The rule of thumb is 1.5" of fish per gallon of tank. So estimate the length of each fish you have, add them all and divide by 1.5. This will give you the size tank you will need in gallons. In a 30 gallon tank you can keep 45 inches of fish (i,e, 45 fish, each 1 " long or 30 fish , each 1.5" long, etc. Do not forget to leave some space for growth of fish.

Thanks for reaching out. The general rule of thumb with good filtration is to have 1 " fish per 12 liters (3 gallons) of water. So starting with 10-15 should be good, but remember babies increase the bioload significantly, so continue to monitor water quality and allow your biological filter time to respond. Good luck.

Thanks for reaching out about your fish fry and including photos of the tank. The tank size should be adequate but also depends on the number of fry being added. Proper filtration and oxygenation will be very important. Good luck.