If it's fuzzy then you have Black Beard Algae. Only run your lights 6 hours but we need some info on the tank. Is it planted? Do you know you nitrate and phosphate levels? Also how often do you do WC
's and how much to you change out each time.
Low light does not cause algae and neither Pleco's or Oto's eat BBA. You can remove your ornament/rock from the tank, put some papertowels in a sink and put the ornament on them then pour Hydrogen Peroxide 3% over it. Then wrap the wet papertowels over it and let it sit for 20 minutes. Then you can just put it back in the tank, no rinsing. The BBA will start changing color red/pink/white within 24 hours which means it dying. BUT unless you correct the problem causing the BBA it will continue to come back.