Has anyone ever tried using something like the compost shower http://www.ecofilms.com.au/2010/06/2...-water-shower/ to heat a fish tank through winter.
I imagine there would be some kind of continuous flow and the water in the pipe would never mix with the fish water, just that the heated water pipe would coil through an insulated (cob?) fish tank.
Would there be enough heat to maintain water temps through a british winter in a portacabin - so not totally exposed to the elements, just using this kind of set up.
am loath to use a water heater, but would like to try some warm water fish.

cheers