Added this along with replacing the cartridges inside with coarse pads, and our Marineland filters became a lot more efficient at housing bacteria. This means that they have more filter power. Took our filters from eh-heh to awesome.
I ordered a large and a medium one, wasn't for sure which one I needed. I needed the large, it keeps all the big stuff out of the filter, it also keep all the babies out. Running on a topfin pf75.
Fantastic service and quick delivery!!