closed loop method

[BBQHILLBILLY]

Im probably turning this into calculas. I probably could just add a mag 18 pump in the sump and feed the 2 1in return holes. Is there something I could get that if the power goes down I wont have 240 gallons of sw on the floor? lmk

Also The only reason I didnt want to do that was because I was going to have an ext return pump 1900 feeding the sump. thats good flow through the sump.
Now add a mag 18 flow thats a lot going through the sump/refug.
Thats why I would like to keep it separate and on a cl.

or maybe not. hmmm

I could use the holes as drains to include a water drain for water changes plumber to ext pump
and then use an two external pvc up around the back and into the tank halfway down for more water movement.