How old is the setup? Add anything new? When I started my tank back in October I had that white fungus stuff growing all over y driftwood, plants, dirt, etc. and it supposedly occurs mostly in newly setup tanks, and is not harmful to any invert or fish you have in there. It will go away in about 2 weeks if this is the case, or you could just take it out (which I reccomend) right now like I did, and I haven't seen it since. Then after that stage, I had my first algae bloom but I took care of that also an now my tank is fully cycled and clean!