i drilled two holes in my tank on the side and used PVC pipes. the pipes run all the way to the bottom of the tank and on top of the pipe where the holes are a drilled two holes. if the power goes out, once the water falls below the drilled holes the water stops flowing. once power is back on the tank refills and the warter flows again. it took a bit to get the water levels right in the sump but i have never had a problem. i made sure i used good silicon on the pipes and have no leaks. when you drill the holes you want to go really slow!!!
im new to this site but i will try to post pic's for you if you want