New aquarium setup questions

[Metromed25]

I just bought a 150 tank that was already drilled with 1.5 inch holes( during a well deserved newbie moment) not realizing it was for 1 inch bulkheads. So no I am planning on how to plumb this for a 55 gallon sump and maybe a diy canister filter. I have 4 drilled holes on the back of the aquarium and one in a weir on the floor of the tank. My goal is a South Americian cichlid tank with g.topajos and electric blue alarms wit congo tetras.

[Flaxon-Waxon]

What questions did you have, if any?

[Metromed25]

My biggest questions is how to plumb the drains and the returns. I am thinking 3 for drains and two for re turns or three for drains one emergency drain and one return. These are all one inch bulkheads. I am also confused on how to plumb the lower holes on the back wall of aquarium. Finally I was planning another big tank [135 gallon] aquarium as a sump with 3 feet of it being an refugium/grow out tank. This last tank was a free on the side of the road addition.

[AquariumExpert]

It looks as if you already have overflow boxes in?

[Metromed25]

Yes, I have one but in overflow, just wondering what to do with the other 4 holes in the back of the tank

[AquariumExpert]

Could I get a full back view if possible?

[Metromed25]

This is the back of tank from side. Two different angles. There is a weir in between the two center drains that empties into the bottom of the tank.