yea i read up on marimo balls, but thanks for the warning, BTW nice biocube!!! do you have any threads on it? i used to have a biocube but i got a different tank and me and my best friend share it at his house! he has better tap water lol that was my problem.Just FYI, my moss balls are major debris collectors. So I don't sqeeze them out into the tank, I sqeeze 'em out in some tank water in a bowl. Dirties the water less (altho maybe not as big a deal if you don't have plants and can gravel vac easier, but still).