I have thought of a similar setup to increase forage in my bass pond. After visiting a koi dealer and talking to Texas Parks and Wildlife and fish farms the setup that I will be trying is the inflatable above ground pools, www.intexcorp.com, from Wal-Mart. They are cheap, come with their own pump and will affix a homemade filtration/areation system. Can be setup in a greenhouse or fashion a cattle water trough heater to maintain temps in the winter.