Pre drilled tank need help plumbing

[Clownsntriggers]

Hi, I'm new to this forum. I read alot in the last 10 hours! I need help with plumbing a saltwater aquarium. It is a pre drilled older style tank with two bulkheads on the corners 1" and has two more in the center of the tank 1/2" bulkheads.

How should this setup be plumbed? Are the two bigger bulkheads used for draining/overflow or returns from the sump. I'm confussed about the this setup to many different answers to this tank start up.

What I think these bulkheads were used for:
1. bigger size bulkheads used for draining with a slip strainer water to wet/dry or sump.
2. Smaller bulkheads used to return the water from the wet dry/sump.

I am open to all ideas.

See pics

 

[SnowManSnow]

IDEA 1
the 2 bigger holes are your DRAINS. The 2 smaller ones in the center would be your returns.

The weird thing is that all the bulkheads look to be on the same level. NORMALLY you put the drains in the bottom of the tank behind a couple of overflow boxes. Maybe someone with more experiance in this sort of thing can help you out more.

IDEA 2
It isn't really drilled for a sump outfit, but rather a closed loop system for water circulation.

B,