Regardless of the gallon size, each will only be able to supply enough oxygen for one goldfish up to 12 inches long. One 30 gallons and another that’s 50 gallons but both have a surface area of 288 square inches. For instance, let’s say there are two tanks. However, it’s important to note that using the surface area rather than the gallon size will support the same number of fish.

This is the most ideal calculation in the event the tank doesn’t have aeration or water flow. This states that there should be 24 square inches of surface area per inch of fish. It comes from a 1948 book called, “The Goldfish” by Harvey and Hems. There is one method people find tried and true. So, 30 gallons for the first fish with 15 gallons for each additional one thereafter should suffice. For Larger Types of Goldfishįor larger types of goldfish species, such as Shubunkins or Comets, the equation must increase because these can reach up to 10 long inches or more. In this case, three fish will fit into a 40-gallon tank. This is going with 20 gallons for the first fish and then adding 10 gallons for every fish thereafter. There’s yet another calculation that seems to be popular among aquascape hobbyists. 20 Gallons for the First, 10 Gallons Thereafter Once they start growing, aerating will be necessary. Alternatively, it may be okay for juveniles without filtration or aeration. In the case your fish are fancy and large, this may be the most ideal calculation to use. But, that means you’ll need a 40-gallon tank for two goldfish. This way, you can anticipate juvenile growth into maturity while maintaining proper water parameters. 20 Gallons per GoldfishĪnother easy calculation is to go with 20 gallons per goldfish across the board. But, this may only be ideal for mature fish, since it doesn’t provide much information for juveniles. This allows for various species, sizes, and shapes of goldfish, including ones with hoods. One Gallon per Inch of GoldfishĪ simple calculation that many people seem to abide is by going with one gallon per inch long of goldfish. While the following calculations are suggestions, you should refer to the specific requirements of your particular goldfish. Of course, the species of goldfish you have and the maximum size they can grow to should be a top priority. Stories and anecdotes abound for a single goldfish living happily in a 2½ gallon tank to a school of 10 goldfish in a 40-gallon tank. It isn’t as important as it would be for something like cichlids. There is a good reason for there being so many recommendations when it comes to gallons for goldfish. So, What Is the Ideal Number of Goldfish Per Gallon Of Water? 11 What Are the Various Sizes of Goldfish Breeds?.10 How Many Goldfish Will Fit In A 20 Gallon Tank?.9 How Many Goldfish Will Be Happy In A 10 Gallon Tank?.8 Proportions Are Somewhat Insignificant.4 20 Gallons for the First, 10 Gallons Thereafter.1 So, What Is the Ideal Number of Goldfish Per Gallon Of Water?.

5 gallon goldfish aquarium