+1 on the Koralia nano 240. I have a 12g tank and run the 240 and the 425. Makes for great circulation and no dead spots in or around my rock work. And since I have 2 and their both part of the new evolution line I can get their wave-maker that runs about $80 MSRP. If you want to do extra filtration try a HOB fuge. That way you can grow macro, which takes away extra nutrients (i.e. phosphate and nitrate) from the water and also prevents nuisance algae from growing in your DT.