Ok, need some help from the experts out there. I have a 50 gal and took a new route from looking after the barb family to platies. Have angles, bala's, silver dollars with platies and my problem is that some of the platies stay just under the surface of the water. All the other breeds swim everywhere in the tank but most of the platies like(?) stay near the top. Temp of tank is 78 degrees, all the fish are healthy, fins are up. anyone know why they like to stay at the top? They have all been in the tank for several weeks now and I am very carefull about changing the filters and water regularly, (with the correct procedures)