Steve
As far as using blue and grey rolls in the bio, I don't feel they will clog if I use the Ultima first, then settlement/mechanical with a touch of bio sprinkled in, before it goes to the bio tank. I'm banking on the water being very clear when entering the bio tank. Also, I'm finding out that trying to get the 37" grey rolls is next to impossible. Both supplier and distributor are out of stock - so, I either buy two smaller rolls and combine them or just use two blue rolls. I don't think I will lose that much surface area.
Mike