your pump can pump more water than it is getting 1.5" pipe will have a flow of 1200gph if there is no 90 degree turns or even if you are useing a flexable hose for every turn add 1 foot to the pipe. you can either add water or leave like it is and use the ball valve to adjust but don't get to much back pressure. I would add more water and a T or 2 going to more return pipes.
Bill