Need help with unknown overflow system

[180gallons]

Hi everyone, I have a 220 that came drilled with a set of overflows that I can't seem to find any information on. It has a opening at the top that seems like it should have something to block fish from getting inside. It also has a double wall with inlets in the front of it near the bottom and about mid ways. If anyone is familiar with this type of setup or know where I can find information on how it works or if it's missing parts your help would be greatly appreciated. I'll attach a few pictures to help.

Thanks

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[180gallons]

Pics

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[duanes]

The small inlets allow water to enter the overflow chamber from mid and lower level, but the main entry is the top (where most pollutants collect (the air water interface)). These small inlets prevent the entire tank from draining, because they are small.
You could put a mesh over the top opening if you have small fish.
I don't see a bulkhead on the tank bottom ( maybe a photo from outside, on the bottom of the tank would give us a better idea of the entire system.
Usually there is a bulkhead that would connect to plumbing leading to a sump.

 

[180gallons]

The bulkheads had been removed before I purchased the tank and all the plumbing will have to be installed. I think I will order new gaskets for the bulkheads just to be on the safe side.

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[BMac91]

Those are Aqueon Megaflow overflows, but someone has modified the top opening. The top opening should also have the small slits like bottom does, but someone has cut them out to make that one large hole. Best bet would be like duanes said secure mesh over the hole to keep fish out of it and you should be fine.

 

[180gallons]

Ok, I feel better knowing what type of system I have. I will have to find something to use as a guard to go over the opening. Thanks for all the help.

 

[DN328]

Depending on how small your fish are you could add black egg crate. Still allow for flow while keeping fish out.

 

[180gallons]

I was thinking about using some gutter guard I found online https://m.lowes.com/pd/Frost-King-Plastic-Gutter-Guard/50031732
Also with all of the filter inlets, I may have to change my pump to one that has a feeding mode because of the flake foods. Right now I have 1 cpr on one end with a wave maker to push them to the other side of the tank but with 2 over flows that will be pulling in through 3 different levels that's not going to work anymore.