Kerrie I wouldn't use the river water without the use of ozone treatment and filtration. There are laws you will have watch out for too in pumping out of a river. As for heating I would run a heap of black polly pipe on the roof and have a thermostat controled circulation pump. I am in Townsville and getting closer to finishing the construction on my fish room it is insulated and I will run a reverse cycle split to climate cobtrol the room.