I have them wide open. I believe its a little difficult to get some flow behind the aqua scape on mine but I haven't had any issues so far with cyano. Just dino, but I seen a lot of people with red sea have dino maybe a lighting thing I have no ideaYa i think my attempt at aqua-scaping caused a few. I've removed some rock but still feel like I have dead spots. Do you have the return pumps wide open or did you reduce it at all via the click wheel thing on the pump? I have them both wide open now, when i first put together i did not.