Uh-oh, I only have 2...is this an issue?
I just wanted to put in my two cents that the oto's will decimate brown algae. I originally bought them to put in my 10 gallon to keep the algae at bay and they cleaned the tank of the nasty brown algae in less than 2 days. After that, I supplemented with algae wafers.
I ended up putting them in my 38 and they keep the glass sparkling eating the green algae too.
Paul