Can I put any kind of a pleco in my aquarium with small African cichilds? There is a lot of brown algae on the silk plants and the castle ornament now. The fish in there (mixed Africans) are all about 3 inches in length now. What happens if I add a large common plec? Will they pick on it? I have a beautiful synodontis cat in there and they don't go near him at all. (7 cichlids and a synodontis catfish in a 37 gallon).