Cary is correct on adding a second disc.That pump produces 2 cfm open flow and 1.8 cfm @ 10 psi, I would be VERY concerned with your stocking rate as it is heavy for your situation, I think with your low water lack of wind etc that you may be headed for the same situation as Donnie Castle(please read that thread on dead fish)The duckweed that were removing some nutrients from the water column are now available to spawn other algae types also.Keep on eye on the CC for piping or gasping on the surface and have a plan ready to go that is beyond just adding a second diffuser, Your demand for oxygen may be fast catching up to your supply, good luck and thanks for posting.
