Return Bulkhead so deep?

[Squiddy]

I just got a new SeaStar tank from Mike at Hidden Reef and have now got it all set up but was wondering why the bulkhead in the overflow box is so low down. If I turn the pump off, 4+ inches of water (90 gallon tank) will drain into the sump, overflowing it.


Showing return bulkhead drilled into overflow box

I know I will need to get some locline or something to aim the returned water but I guess I am going to have to bring whatever line I have coming out of there, up to the surface so that only a small amount siphons back into the sump. Any suggestions?

Also, the drain standpipe seems to be sitting quite high in the overflow box. I screwed it down as far as I could into the bulkhead in the bottom and the rest of it was already pre-glued but right now if I open the return line up fully, the level in the tank goes too high and looks like it might overflow. The pump I am using for now will do about 500gph at 5ft.


Showing temporary sump and flow restricted with ball valve


Showing where return and drain lines come through bottom of tank inside overflow box


Showing view from inside overflow box of return line (reflection) and top of standpipe (right)

I assumed that these kinds of things should have been already set from the factory. I will obviously have to lower the height of the stand pipe which will unfortunately require cutting and rejoining the pipe because everything is already glued together.

Am I doing something wrong here or is this pretty normal? My previous 90gal wasn't drilled so I haven't had to deal with this kind of thing before. Please help. Thanks