Help a newbie plumbing! Herbie method

[xaacuetara]

Hi guys!
I recently bought a new tank, now I’ve been working on plumbing it for a couple days and it’s almost done!
Just came across some concerns I noticed my overflow box has water intels above and below (like the drawing I attached) so I’m concerned that my main water drain PVC will drain a lot of water of the display tank In case I turn off the pump, so I’m looking for advice should I just add more height to the main drain line? Or block the low intel.
This is my first time plumbing and don’t want to make any future mistake that will cause headaches
Thanks for the help guys!

 

[TX_REEF]

I'd personally block the lower inlets. with the current setup, if your return pump in the sump powers off for whatever reason, your display will drain to the bottom of the hole in the glass inside the overflow box, whereas if you block off the lower inlets, it will only drain to the bottom of the top weir. This few inches of difference can make a big difference in how much water your sump has to handle during an outage, depending on your display tank size.

 

[Aquavaj]

I'm pretty sure those overflows with the inlets at the bottom have a glass backing inside that goes up to near the top. If it didn't then your whole display will drain through the bottom inlets and all into your sump.

 

[xaacuetara]

I'd personally block the lower inlets. with the current setup, if your return pump in the sump powers off for whatever reason, your display will drain to the bottom of the hole in the glass inside the overflow box, whereas if you block off the lower inlets, it will only drain to the bottom of the top weir. This few inches of difference can make a big difference in how much water your sump has to handle during an outage, depending on your display tank size.

Thanks for the answers! I decided I will do that, blocking the intels seems the best option :)