I noticed this white fuzzy build-up on my fish tank filter right where the water flows back into the tank...is this bad?? I change my carbon filter monthly and a water change as well. My fish don't seem to be affected by it but I want to make sure its not harmful??
The buildup may be indicative of over feeding or over crowding. Try to feed no more than the fish eat in a couple of minutes, and change about 20 or 25 percent of the water every week. If the aquarium is operating close to its biological load limit, more frequent partial water changes may be necessary.
Changing 30 percent or more of the water can produce sudden changes in water parameters. Such changes are very stressful for the fish and could make them vulnerable to diseases and parasites. Small, frequent partial water changes are much less likely to produce sudden changes. The replacement water does not need to be at precisely the temperature of the aquarium, just roughly the same.