Well that depends on what kind of power head you put in there. And if you have a reef tank and LR then you should have some snails, and hermits for your clean up crew its pretty much a must have. I have a 29 gal cube with an upgraded power head as the main pump and 2 powerheads inside the main tank for circulation.. But in a 12 gal it would def depend on the size of the power head but generally speaking an extra one is always a good idea.