Thanks for the article link - that's the info I was looking for. I wasn't sure what kinds of media there were that would fit into my box filter. I checked a catalog and have found some BioGlass noodles that I am hoping will fit. Or maybe I will switch to a sponge...
TankGirl - thanks for noticing what tanks I am running. I use the box filter in the 10 gallon, which now sadly only has one puffer left. In fact, I just wondered if there was in fact a minimum bio-load for a tank. Hmm. The idea of a sponge filter sounds good to me, altho it seems like it doesn't do much (if anything) for mechanical filtration.
How often should the sponge be replaced?
Oh, and the 29 gallon, well that's another post, because I have been thinking of upgrading that filter, too (no, it's not a box filter!)...