20XH tank. 1 15watt 6500K screw in cfl, 1 20 watt cora-life bulb. Not sure what the K rating is other than I was told it was full spectrum for plants ( it has a pink tint if that helps), DIY CO2 and a few root tab ferts in tank. I "giant val", 1 anubias nana ( pardon the spelling, new to plants) and 6-7 water sprite floating. Everything sees to be moving along nicely. I have notices a fine covering of brown algae on the stones in the tank but didn't worry about it since it gave it a kind of "au naturel" look and wasn't on the gravel. However last night I noticed small spots of it starting to form on the glass of the tank. It wasn't a big deal and came off with a simple swipe of the tank cleaner. I know algae tends to come from an imbalance of something in the tank. Suggestions on what I could or should be measuring to find out what may be in excess to cause the algae?