In my 56 gallon freshwater tank, I have 2 Penguin 200's moving water as they filter, but I've noticed a "dead zone" behind some of the decor (that my wife insists we keep in the tank) where the water doesn't circulate up and into the intakes of the filter.
I was thinking about putting in an auxiliary pump to move the water in that area to help keep the debris and detritus from settling to the tank floor. My two candidates are either:
A Koralia Nano 425: Hydor Koralia Nano - Bulk Reef Supply
A Koralia 600 (or 550..): Hydor Koralia Evolution - Bulk Reef Supply
My primary concern is the flow rate. I have some high fin tetras and a bunch of rainbows. I don't want the current to be too strong, but I want it to be able to stir things up enough to get the stuff into the filters.