I notice that my water bottle baffle had mold in it so I took that apart and then notice it was coming from the filter. So I shut the filter off and I wipped the mold off. I don't wanna replace the cartridge sine the beneficial bacteria. What could the mold be a sign off? The tank is about 2 months old. I cycled it for a month. I did have a problem of foggy water. Other than that the parameters of the water are all where it should be the water is crustal clear, I do 50% water changes weekly and a 10% water change mid week. It is a ten gallon with a divider.