All I need is a small drop in temp. I have used the cooler extensivly on the boat. It will drop the temp about 40 deg with a very low draw at 12v. For the tank I just need a small drop about 5-10 degrees. I have not looked at the smaller units, but the plan is either direct plumb it in line as a cooling tank or run some coiled plastic tubing inside. The tubing will definatly insulate the water a greatly reduce the cooling effect. In line the water will flow thru quickly so there cooling effect will not be that great either. I could also possiably run it off a small power head for reduced flow.
Who knows, it's just an idea in the planning stage. I will post any updates.