Yes every now and then I will see some fine mist bubbles in mine..Not that bad. Give the canister a nudge and you will hear a burst. My 404 is not that bad but my old 204 got bad and I retired it and got the newer and larger 404. More Power and crystal clear water. 8)
50 gallon saltwater fish only...1 mated pair yellowtail damsels, neon dottyback, tomato clown, huma trigger, lemonpeel angel, 12 stripe wrase, bi-color blenny, dozen or so hermit crabs-scarlet and mexican, cerith snails, turbo snails, orange linkia starfish, 50 plus pounds of purple-pink coraline encrusted rock and a few mushrooms.
Redsea prism protein skimmer, 404 Fluval, UGF
with two 201 powerheads.
7 gallon tank with 6 pounds of live rock and countless brittlestars, 5 hermit crabs, snails and 1 False Percula Clown fish and Camel Back Dancing shrimp