Suggestions and help with plumbing my tank please?

[untamed]

Sorry about that...I missed reading the text below the picture about the overflow box (or lack thereof).

OK...if the upper hole is a drain...then you can make the lower hole a return/input. With the low hole being an input, you would have to be very cautious about controlling backflow in a power failure as it would drain your entire tank back into the sump!

While a check valve works, you might just consider blocking that lower hole all together and running the return over the top edge of the tank. It's just safer.

Given you have only 1 hole to work with to feed your sump, I would run some form of the modded Herbie as discussed on this link.
http://www.canreef.com/vbulletin/showthread.php?t=39629

I am concerned that you won't get enough surface removal without some sort of overflow box...or you'll end up with a really noisy drain...

[Jason McK]

I think the best use of the lower hole would be for a closed loop. If you wanted to go that way. It could draw water through a pump then returned with plumbing over the top of the tank.

I would not recommend using it as a return. Power goes out and you'd have 120G on the floor.

I'm no expert in overflow design, typically I've always built a box. Untamed is the Herbie expert.

J

[mark]

Don't use the lower hole for the drain even with a check-valve, unless you say have a 90 then extending upward to some form of overflow. The overflow does not need to be a box going all the way down but could be a coast to coast style tying into the bulkhead or could also consider just a piece of horizontal PVC (pictures here).

Upper hole for return.