Hello Mandrew, on my 90 I'm running a WP40 and a RW 15. The WP 40 is mounted on the right side of my tank and is set on else mode. The RW 15 is mounted on the left side and is set on the constant mode running at the number two speed. The RW 15 replaced Two Koralia 1400's I had mounted on the left side of the aquarium.