Hi Mark.
similar enquiry from a fish tank nut with no money, suggested passing flitration water circuit through a bucket of water in a standard refrigerator. Plastic pipe coiled in bucket, add some ice for peak loads. Worked a treat. Punched a couple of holes in side of old refrig., was only necessary in summer peak loads. He spent $50.00 on an old refrig., kept his beer in it as well.