I used my shop vac with filter media on the bottom to vacuum up acorns and debris from my pond bottom and used an extension pipe from the vac drain to return the water to the pond, then after getting all of the gunk out I do a water change. My question is, Has anyone figured out how to vac and drain simontaneously to eliminate the start, stop, drain, start.......? I tried putting a ball valve on the drain to try and balance the inflow with the outflow and it helped but didn't solve the problem. Next time I will try putting a 90 on the the drain pipe and extend it down below the pond water level to maybe keep the vac sealed on startup? Anyone tried anything that works great?