The lfs guy asked me if I had green or black algae when I asked about a pleco, but I had the kids with me, and things got crazy, so I never got an answer. I have green algae on the glass but black on the ornimants and plants. I had a pleco before, with no problem cept the growing thing, he did great keepeing the glass clean, till he got too big. had to take him back. I'd like to get another one but am woried about the algae thing.