Pluming challenged and a DIY solar heater

[pool-at-wwworkz.com]

I am looking to add a passive solar heater to my existing large (approx 26000+ gallons) above ground pool. I would like to to add several standard return (from filter) type fittings near the surface, and also near the bottom of the pool. Is there a way to add these return lines near the bottom of a full pool? I know I could drain and re-fill the pool, but that would require several hundred dollars of chemicals to remove the iron from the new water, and also concerns me because the liner is several years old. Any advice would be appreciated. If you know of a product made for this use thet would be even better. I want to use return type fittings because I can easily buy plugs to close them for the winter. Freezing happens.