I've noticed the past month in both of my tanks that there is a fuzzy white mold growing in the filters. It's above the water line in the filter on one tank and on sponges in the filter that are not completely submerged. On the second tank it's also growing on a sponge i have positioned on the outflow, the mold is growing on the part of the sponge that isn't in water. It's also underneath the glass lid around where the water outflow is. Any idea if this is harmful and should i get rid of it? It's definitely not hard water deposits, it's fuzzy.