talked to one of my friends whos into engineering, but i may have found an efficient way to keep the tropical pond heated. he said itd be pretty easy to insulate even a steel building, and that that would also prevent it from overheating during hot days, but to build them like 3 feet into the ground, so they are even further insulated, and to do water heating coils through the walls of the pond, and that can be set to a constant temperature for heating, dont know that if i put the two ponds adjacent to one another, if the residual heat would keep it warm enough for the koi pond to not freeze, but im not against a unit space heater in there either.
thing is, this is one of my best ideas and i really want to do it, and i know that it can be easy to obtain and do, i just really want to make it work.
one, its not as expensive as buying a smaller acrylic tank for a few fish.
two, i can keep lots of fish that i never thought id ever be able to because of their size, like the rtc and tsn
three, it is easily obtainable financially, all id have to do is get it built when they set it up, and just add the filter and cycle it well, get all the components going, and wahlah!