[rockworm]

I have had a 90g and I used the SCWD. At the time, I used it for some water movement in the dt. In my opinion, it is not necessary. It helps add a little random flow, but I feel that powerheads work better. They can be added or removed as needed. You can change direction of water movement by adjusting the heads. I now use controllers with powerheads to create the random flow. I see the return pump as a mechanism for water exchange between the sump and DT. It controls the rate of water through the sump where all water quality work takes place (e.g. skimmer, heaters, reactors, etc.)