I’m cycling a 20 gallon (76 liters) tank and I have 3 mollies currently. As the tank is done cycling, I want to add more mollies and glofish! How many of each do you recommend?

  • I have about 100 black mollies in a 29, the majority are young of various ages. That is too crowded to grow well , but they look happy . Depending what kind of dyed fish ( glofish) you have ( tetras and danios are common) they will likely eat the baby mollies so you need not worry about getting to my situation. Dec 1, 2018 at 1:31

1 Answer 1


While a 20 gallon (76 liters) aquarium is a great place to start, most species of molly fish would thrive in something larger. This is especially the case if you plan to own a significantly larger number of molly fish, or if you wish to mix molly fish with other fish breeds.

From what I've read, 4 to 6 mollies is an optimal number in case of a 20 gallon tank.

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