150g Cube Build - New Pics

[golf nut]

It's a bit of an issue, if we get the Dart to run full capacity then likely your overflow will not handle it, I would plumb 1 1/2 all the way to the surface then tee off the 1 1/2 pipe to get a total of four 3/4 returns, send 2 to the bulkheads and the other two would have to go over the top. when it comes to volume you need four 3/4 outlets to handle that pumps capacity

you may have to throttle back the pump to keep the sump from draining, and the tank from overflowing