I have a piece of driftwood in my 55 gallon tank with 5 young adult tangerine/pigeon bloods. Some green algae looking stuff has completely colonized the driftwood and I was wondering if anyone knows if this is good or bad and what i should do? They seem to be eating it and I don't know if I should leave it. I also have a problem with my pH. I am filtering with peat pellets and I can't seem to get the pH lower than 7.6. The discus seem to be ok other than they don't eat very much. What should I do to lower the pH without doing harm to the fish? I have discus buffer but when i used that before it killed the single pigeon blood that was in the tank and seems to have permanently done damage to my young cobalt blue because he hasn't grown at all in 3 months.