I prefer dry skim. I don't know why, but I like the looks of thick, black skimmate... rather than the pale, watery look of wet skimmate. I suppose I like it better because I'm basically removing the same amount of organics without losing as much tank water. I clean my cup and neck once a week... every Saturday. It's an 8" cup, and it's usually 3/4 full (dry skimmate). It would probably overflow in a week's time if I ran it wet...