Glad for this post as I am having the same diatom trouble in a 35g well-established tank. Perhaps I should turn the lights off for awhile... very frustrating.
37 gallon community; 10 gallon S-SS CRS; 2x10 gallon guppies; Specialties: Japan blue guppies (wild type), Ginga sulfureus guppies, Blond platinum LS guppies with purple mutation.
Non-aquatics: Off-track thoroughbred racehorse; 2 Maine Coon-type cats; 70 orchid plants.
12G Rimless Club