Preformed plastic pond

Hi! I'm new to this group. I recently joined because im wanting a pond in my garden have a preformed plastic pond unfortuanately restricted on space & was going to build it in some big wooden plantersive got but they are too small I cant dig it out to go into ground as alot of concrete from next doors garden has come under the fence. Im after advice please the pond is 50" x 35" x 16". Thank you