FWIW - I use my diatom filter with every pwc
just to clear up the water and polish it (in my fw
tank). You wouldn't want to run it for any length of time because they clog up after 12-24 hours. The benefit of using a diatom filter is that it will remove tiny, tiny particles and really clear up (polish) your water. I've heard folks say that it will even remove ich from tanks. If you can get one for cheap I'd jump on it otherwise it's not something I'd run out and buy right away.