The mini-Remora is supposed to come out soon; that might be good (at least if it follows its larger cousins) and fairly low cost. Prizms are good if you're careful about husbandry (diligent water changes, low stocking levels); more like a back-up and confidence booster than an actual filter, though (however, they make great places to put carbon). I have one on my 10, and it looks great, but I doubt the Prizm helps a lot.