Yep Anon's right. 20 fish is the limit per tank. If you want to breed so many fish at one time, divide the fish up between two or even all three tanks I usually put five pregnant fish in my selling and second tanks, and put any others I have in my first tank Putting pregnant fish in the selling tank is especially good if you want to sell your breeder fish as soon as they've had babies, since the babies don't get sold. Since I usually have alot of fish at one time, I generally move all the babies to the selling tank when I'm waiting for them to grow ^_^ That way, if I accidentally hit the 'sell' button, I don't lose any fish by accident >.< It's happened before O.o Good luck! ^_^