Fungus growth on Gravel

Question
I have a 20L freshwater tank that I set up at work. I have 3 danios, 3 cory's, 5 neon tetras, 5 cherry tetras (all small size) and 2 African Dwarf frogs.
I have a bio wheel filter (20 gal) and a 10 gal carbon filter on the back of the tank as well as an undergravel filter and a powerhead and a heater. I change the filters once every 2-3 weeks and do a 40% water change every other week. I feed my fish and frogs every other day. My fish and frogs appear to be healthy but I have trouble with cloudy water and now I have white, cotton candy looking stuff growing attached to the gravel.  I tried siphoning it out with the gravel siphon but it's attached and won't come off. I test the water weekly with multi test strips and the water seems fine but leans towards high alkilinity and hard water hardness.  The environment the tank is in is temperture controlled during the day, but at night and on the weekends the building air-conditioning shuts down and the tank water heats up to 82-84 degrees, maybe warmer when it's really hot. I turn the light off and open the top to help cool the water.  The water heater is set for 78 degrees.  I feed my fish flakes, mini tabs, tadpole pellets and sometimes bloodworms and brine shrimp as treats.  I condition the water with stress coat.  I hope this is enough info for you, if not let me know.  Thanks


Answer
Hi Jayne,
Sounds like you just have a common aquarium fungus going on in your tank. It usually appears whenever a piece of fish food goes left uneaten in a crevice of the tank. The fungus gets ahold and often can be difficult to get rid of. But removing as much of it as you can (even if that means taking the gravel that its attached to out with it) and doing several good  (30-50%) water changes with gravel vacuumings it usually disappears. Sometimes its a sign that your tank needs more frequent gravel vacuuming and water changes. Maybe try doing your tank every week instead of every other week. That might help.

Best of luck with everything!
Karen~