newby needs help..why do all the fish hide in the back corner next to the air stone? why does the serpae tetra have a white bottom lip now? we have a 20 gallon tank with 1 pleco 1 serpae tetra 3 black skirted tetras 1 white cloud 1 african dwarf frog 2 red unknown fish and 1 gold barb...is this too many fish? they are all small except the pleco who is about 3 inches long. Thanks for your help. My daughter and I are trying to keep fish for the first time - someone gave us their tank, fish and all.