Yes, you can have more than one BN pleco in a tank. I have tanks with up to a dozen in them. My tank with a spawning pair has about 50 fry in it right now, in addition to the parents.
With algae growing on the glass, you should probably cut down on the amount of light you are giving your tank. If it is in front of a window, you will have to block the back with black poster board. Unless you have live plants in the tank, you should only have the lights on when you are there to watch the fish. They do not need light to do their fishy business.
You should probably cut down on the amount you are feeding also. Feed only once a day and only as much as they will eat in 2-3 minutes. Excess food will decay into ammonia, nitrites and nitrates that are all toxic to your fish. Nitrates are what algae uses as food, as do other live plants.
You should also be doing 30% partial water changes every week to keep those three chemicals at or near zero levels. |