I did that as well before I sold my FX5. Just hooked it up and pumped the water out the front door!!!I use my FX5 on my 135 to drain to the tank. Hook up some 1" ID hose to the spare aqua stop valve the FX5 comes with and you can drain 900 GPH lol. Then I use the hose to fill the tank back up. On my 120 tall I use my python.