Looking for some guidance. My 36 gallon fowlr keeps having tons of red cyanobacteria (think that's right) and green algae. Do 20% water change every 2 weeks. Have 4 or 5 snails and 2 emerald crabs. Only have 2 damsels in there. Treated the tank 3 times now with Chemiclean, did water change as directed each time. The dude at the fish store said I would be fine with a hang on back filter that I think was for 75 gallons, so that's all I've had on it. I clean it out and it comes right back within 2 weeks. Suggestions?