Just curious if anyone using a canister filter notices air trapped in it. I use a Magnum 350 on a 100gal planted tank, and air usually fills the top 1/4-1/2" during the morning (and 1"-1&3/4" in the evening). Any ideas what is the cause or how to prevent it? Curious what you all think. Cheers, Mark ------ pearlsco at u_washington.edu How much does a fish need a bicycle like a man needs... ?