To answer your question I did a quick search with Google. I skimmed 4 or 5 different sites (one was a link to a thread here) that stated otis will eat brown diatoms and should consume it very quickly. I have 4 in my 50 gallon planted tank. Unfortunately, they don't eat the algae that I have but I also have other bottom feeders so I feed a little extra flakes and use a sinking food. My otos seem to be happy and I have less algae than I think I would if I didn't have them.