I think you need to start a list of everything you would need to actually do this. It seems like it could easily take over $6K by the time you buy a pond, pumps, filters, heaters, building materials, etc. I would guess that just for a proper build for a secure enclosure with pond. It may be cheaper to move to Florida.
I would also start checking out what this is going to do to your trailer. Having a pond in the room that is going to need heat Im sure will make a very sauna like climate. I can not imagine doing this would be good for the room.
One other thing I would not want to risk is having a seam in a two piece pond inside my house. I don't see you getting a proper sized pond inside the trailers room without going with the two piece models. Then there is the issue of the weight on the floor.
There are a ton of things to think about, plan, and research with this. I don't believe you have scratched the surface.