I was wondering if I could get away with this. I have a 120g African Chiclid tank. I used to have a Fluval 404 and 2 Pen. 350 bio wheels and 2 Pen. 160 bio wheels on it. About six months ago I took off the 404 and put on 2 FX5. Now my question is would it be OK if I take off the HOB bio wheels and only run the 2 FX5's? BTW I have only 12 fish ranging in lenght of 2-5 inches.