now thats real algae ....i know you said your careful about feeding but that is a big conteibutor most of the time...RO will help for sure ....is the tankexposed to natural sunlight {that will bloom algae as well} there are crabs and such that will work on Cyano algae/bactieria...if you have a pretty hefty filter you can take a turkey baster {not you wife/girlfreind/sig other or moms....lol} and gently blow it off everything ever day or so and let the filter work on it

if you have white lights and actinic you could cut the white ones down to just a couple hours a day for a while as well........the blue light doesn't have the spectrum to be a benifeit to algae ..........

Boss

I have 2 walmarts as well ...one has the culligan machine and the other doesn't ...if you can't find that machine the "Value" brand {wal-marts brand name} 1 gallon jugs with the green label are RO filtered {the blue label is UV filtered} and they are about 66 cents a gallon ...Boss