Overflow vs 2 holes drilled as overflow

[milkman]

My friend has an acrylic tank he drilled 2 holes at each corner to replace an overflow box. He says it works perfect which it does, but what is the difference between an overflow vs 2 holes drilled as an overflow?

 

[milkman]

Bump to the top.

 

[am00re34]

if he is sucking water through the holes and running it down to a sump it pretty much serves the same purpose. The main downfall of his plan however is your sucking up water from the bottom only. Overflows usually have intakes at the bottom, middle and top. And the top is usually where the majority of the "crap" accumlates and thats what you want to get down to your skimmer.

 

[milkman]

One downfall I can think of is less flow with 2 holes drilled in the back vs the overflow box. There's always a chance a snail of fish could block the hole and cause your tank to overflow.