I've read that Otos are somewhat delicate, as far as water quality is concerned. I've got several (10, to be exact) spread between my two tanks (70 & 55) and don't have any trouble (despite having extremely high nitrates). They are much, MUCH better algae eaters than my 13" Pleco. The Otos max out at about 1 1/2" and are very active fish. One might even describe them as nervous. Some of mine are nocturnal and some are diurnal. Not sure why. I don't have any brown/diatom algaes. All green, mostly short or long hair. On the glass, the threads can reach 1"+ and on the leaves it seems to stay short (<1/4"). The Otos don't discriminate, they just decimate!