I use AI 32 HD X2 on my 120. Place them in a cave or underhand. A shadowed position. Medium to low flow so they can catch food. Twice a week feedings. I have 4 very big clusters of them in 4 different positions. Biggest cluster has about 30 heads, smallest about 15. If they are well out of the light they will open all day long. If not only at night.