I always see questions along the line of; Should I add pump to make my chaeto tumble?
I don't want to get into the discussion whether that's required/good for chaeto growth here. I just wanted to point out that usually the flow through the sump is enough to make chaeto spin. The flow just needs to be the correct shape: laminar flow along one of the sides of the chamber.
Here's the example of my chaeto spinning by just restricting the flow of the standard Waterbox fuge and creating a narrow laminar flow along the bottom. The orange acrylic is restricting the slits in the glass. By restricting the flow to a more or less narrow hole I can control the speed of spin.
I don't want to get into the discussion whether that's required/good for chaeto growth here. I just wanted to point out that usually the flow through the sump is enough to make chaeto spin. The flow just needs to be the correct shape: laminar flow along one of the sides of the chamber.
Here's the example of my chaeto spinning by just restricting the flow of the standard Waterbox fuge and creating a narrow laminar flow along the bottom. The orange acrylic is restricting the slits in the glass. By restricting the flow to a more or less narrow hole I can control the speed of spin.