I have a 55 gallon tank 48Lx12Wx21H. My filter is a hang on Aqueon quiet flow 55. I only have 3 fish - 1 common pleco, 1 dojo loach, and 1 glass cat. I had more at one point but they died. I know the loach and glass cat need friends and they're coming soon. But before I can add more I need some...