I have like 3 powerheads in my tank (29)...and still have one dead spot...it's too small for me to really care too much, I just routinely suspend the ditritus. I think that more importantly you need a lot of flow dispersal...meaning more powerheads in a tank like that. Instead of getting one big K4, I would go with 2 to 3 twos. I have one koralia 2 and plan on getting another soon. That with a 160gph ph will be enough flow for me.