Hey, I am trying to get the micro sword to spread across the bottom of my tank, but it keeps getting covered (as well as other areas on the bottom) with a layer of "mulm". Does anyone else have a problem with mulm (ya know, the stuff that looks like a lot of fish poop)? I don't have that many fish. I clean weekly, and have pretty good filtration, but it doesn't really make a difference. Thanks, Jeff