help with tank setup and ideas

[mr_alberta]

Why do you have an overflow box draining into another overflow box? Anyway, if you want the water level to be the same on both sides, you'll have to raise up your durso. The water level is usually at the top of the elbow on a Durso. The way you have it drawn now, you're internal overflow box will be loud and suck in a lot of air which will get sucked into the durso in the external box and cause a lot of gurgling and splashing.