I had originally bought a Marina i25 filter for my tank, and another a month later (total of 2) but two months later the first stopped working for me. at all.
I decided to use a sponge filter and got an aqueon air pump and some big ol' filters off amazon. I have the remaining Marina in my ten gallon since it's the biggest I have and it has two fish. I put the sponge filter on the other side of the tank in an attempt have it not cycle all over.
10 gallon has two filters (one cycled Marina, one brand new)
When is it safe to put the marina filter back where it came from? (It's a smaller tank so its not so much to change)
Sorry if this is confusing!