If you decide to try gyres again mounting them up and down in the corners of the tank. This has done well for me in my 25g lagoon. The lower half shoots straight forward towards the front glass and the upper half is angled in across the rock face. I get tons of flow this way.Trying Tunze 6040s, quiet so far and seem to move a lot of water. Should all but disappear when they get coralline on them.