first fill-up, new overflow

[chefbill]

OK I think I'm over thinking this, but I'm confused. I have started filling my new 90 gal corner overflow. My question is how much water in DT, in sump and in overflow before turning on the pumps? LOL this wasn't a concern on my Biocube.

[mr_X]

The dt will need to be filled until it's running over into the overflow, the overflow should be filled as well, and the sump should be filled to wherever point you have figured out to be the ideal level to be. All compartments will be filled to the top of the partitions except for the return compartment. This is where you will have to leave space for when the power goes out.

[chefbill]

OK. When I cut my sump baffles, I left a space between the top of the baffle and the top edge of tank. Should not change the functionallity of the tank, but will give more room during an outtage.

[mr_X]

You still need to make sure your return doesn't back siphon more than the sump can handle. Have you done this?

[chefbill]

I havent turned anything on yet. Just about to start measuring salt. I know, but nothing alive in tank yet, dry sand and dry rock. From here on out, all water will be mixed and cured before adding to the tank.

[mr_X]

If your return nozzle is 3" under water, it will back siphon that entire 3" of water into the sump in the event of a power outage until the nozzle starts sucking air and the siphon breaks. UNLESS for some reason it starts sucking air sooner. One way to do this is to drill a small hole in the return just below the water line inside the tank so that it will suck air almost immediately in the event of a power outage.