Jbj 45G rimless tank--3 small holes on black wall?

[hipertec]

Just picked up a jbj 45G rimless AIO. Before I start to fill the tank, on the plastic black wall, there are 3 small holes that goes to the back chambers from the main front tank area. On hole on right, center, and left area about 1/3 up from the bottom.

Should I plug these 3 holes from keeping the water from the main tank going go the back? Best way to plug these holes up if it's a good idea? Not sure why they are there. To me, it just keeps the water from going thru the top areas and thru the pumps.

 

[Danny_15]

I could be weong but maybe they are for the return pump

 

[Grootzilla]

Could you post a picture of the holes?
They honestly just sound like a part of the overflow but perhaps not.