I used to have a small bit that just showed up in one part of my tank. I lowered the amount of time my light was on and got some small crabs to pick at it. Lowering the amount you are feeding is a wise idea much like the above post stated. If you do water changes you can suck the stuff out, try and get the bubbles with it to help slow the spreading. My first mistake was draining too much water while trying to clean the tank, if you drain too much water it will just keep comen back.
