I have a 84"x48x30 indoor pond I built about 1.5-2 years ago. Its wood framed with insulation and a epmd liner. Just needs broken down. Its built with screws so it can easily be taken apart. $200 obo..
Not much to look at, but it gets the job done. The back panel is insulated inside and out. I never got around to doing the other sides, the foam insulation on the inside does a good job. I kept the water at 80 degrees with no problems. The outside could be finished with wood panels to make it look nice.