I recently got a 55 gallon tank with 4 Oscar’s. I know it says they need 75 gallons per Oscar but has anyone been able to have a few or four in a 55 gallon tank for a while? They are a few years old now I think.
I’m not talking about tanks that are too small for the fish, but tanks that are ‘big enough’ and then even bigger. It’s about stress, which inhibits growth hormone production. Some fish are stressed by a tank that’s small, and won’t grow, and some are not stressed and will continue to grow. Growth hormones affect the whole fish so if the fish isn’t growing, the internal organs aren’t growing either. Oscars for example will generally grow to about 10” os so in a 4x2x2, and about 12” in a 6x2x2, which I agree is a minimum for four. In an 8x3 they’ll grow a bit bigger still….No it's not true that fish will only grow to fit the aquarium that they are in.