hey i have a 55 gallon and have 7 rainbows (the biggest is 3 inches),3 small catfish,5 gouromis,2 angelfish ,4 danios,rainbow fish,1 pleco and 2 german yellow rams ther all about 2 inches or more, the gouramis are abou 4 inch. and a blue crawfish hes about 3 inches hes peaceful though,i moved all decor to the back of the tank so theres alot of swimming room,im using a marineland bio wheel 30 and a marineland magnam h.o.t filtration unit and i have 2nd unit a EHIM but its for use of 25-30 gallon tank it helps though,am i ovestocked ,and my 2 german yellow rams are loosin there color one day and they get it all back the next is this a ph issue or stress.thanks for your replies