We have a 75 gallon with a Tunze 6000 on a single controller, but no closed loop. We are using a SCWD coming out of the sump. As soon as we make room in the rock we want to add another 6000 on a multicontroller. A single 6100 in this tank would be a gigantic amount of movement in one direction, so we want to opt to have two smaller ones aiming in different directions. Our tank is an LPS tank primarily. I know it is more expensive, but I think for your tank it is a better option to have 2 6000s on a multicontroller. Also depends on what kind of flow comes out of your sump and if you also have a closed loop and how big that is.