At what rate do these fish grow. I have a 29 gallon tank and was wondering how long i could keep a pair of one these(maybe eve just a single oscar or jack dempsy) until i had to get larger tank. There would also be a catfish? I cant really find any copmatible fish. Does anybody else have these fish with other fish or critter in the tank with them. I guess i was wondering if they would eat a crab or crayfish?