I wanted to setup multiple aquariums for breeding & simply to have all the fish I want but can't otherwise. I'd rather have a single filter for ease of maintenance but then this causes obvious problems with different temperatures & any disease breakout.
An air system would be a solution to this but they're noisy?
I've seen on top filters. I don't mind if it is the case of just taking out the sponge cleaning it and putting it back again.