I'm currently using a 1000w allied precision bucket heater, $40 from amazon.com in my 1,000 gal indoor pool. I'm going to get the JBJ true temp controller rated for 1000w soon from fosters and smith $79.99
It's not really possible for me I live in the nw and it's pretty cold In the winter I wouldn't be able to heat the garage it's in I was also wondering what till I do to keep the fish from jumping out of it