Larger tank question

Hi! Ok so I have a 65 g hex tank that is very hard to take care of. I got it used 3 years ago to see if this hobby was for me. I currently have hanging from it two biowheels from my magnum, a heater, a protein skimmer, and an extra powerhead. I have a nice coralife light. I have only one damsel, one peppermint shrimp, one electric blue crab, one red hermit crab and a very evil crab of unknown species that has been picking off my shrimp and all of my other slow moving critters. So I want to get a 150 gallon aquarium with overflows. (I am thinking of the future here.) I know what tank I want and stand. However, to save money now I was wondering if I can keep my 65 gallon intact and run the hoses from the 150 through a wall to the 65 gallon in a storage sink area and then return the water to the 150 back through the wall. Maybe add on a uv sterilizer and what ever else needed on the 65g until I want to add more livestock to my main tank. I know my magnum is not meant for 150 gal tank but if I don't add anything new will it matter? Thanks!