Diatom filter?

They do work. If you turn it on overnight, it will collect all of those junky little particles floating around in the water that pass through the regular filter media (the dust & bubble looking crap) It will make the water look crystal clear. They clog up fast & are not for 24/7 use. Maybe one night a week & then you have to clean it.

You can get micron paper filters that work nearly as well & they're a lot less hastle. I use the paper cartridges for the magnum 350 filter & they're pretty effective in my freshwater tank. After I'm done with them, I dunk them in bleach overnight & let them dry out. Its a lot easier than messing with powders.

You can also get some micron cloth pre-filters that you can put between your filter floss & chemical media. Depending on how mechanically efficient your filter is, this can work fairly well. If you can get this to work, its cheapest option, since the cloths are like $4 for a 10x18" reusable pad.

They don't add much value besides crystal clear water. If you don't mind some crap floating around, then skip it. They can be good at removing floating algaes also. They're like the finishing touch on a good system... not the first thing you should spend money on, but its a nice addition.

i used to maintenance fishtanks for a living, and used a diatom filter after everything else was done while i was cleaning up. they definatly work, but i wouldnt use one on my own tanks, because its honestly a pain in the buns and my tanks look good anyway, if you go out into a river or the ocean things are never as pristine as they are in a fishtank anyway, so why bother , the fish wont thank you

Ditto to what vort said about how they work and their use. Are they worth it? Only if you want or need a highly polished tank. I have used them in the past but only very, very rarely now.

MM