There are a couple of above ground heat pumps out there...
I know aqua-pro name & jandy name brand makes one; perhaps additional companies as well...

http://www.bestbuypoolsupplies.com/heatpumps.html

http://www.realpooldeals.com/Details.cfm?ProdID=771

http://www.cheappoolproducts.com/Aqu...2~product.html


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http://www.waterwarehouse.com/products/sku-5616.html

http://www.zodiacpoolheating.com/products/hp70.asp

Plus I think some of the smaller ig models are able to be used with ag pools

Best of luck!