Question on overflow

[luckyk0505]

Hi

Im interested to buy this used fish tank

its 220gallon with center overflow box. but unlike other one

this overflow doesnt come all the way down and it has 2 1" hole

in back of the tank. I thought most tank has hole in bottem of the

tank. its this normal?

 

[mike tv]

the back drains are actually far more common

 

[luckyk0505]

Oh thanks. so how much flow can that handle? less or more?

 

[luckyk0505]

how come its first time for me to see overflow like that

 

[AZDesertRat]

Chances are the tank was not drilled from the factory but was done at a later date. Most tanks have tempered bottoms which cannot be drilled so a previous owner probably added the internal overflow and had the back drilled.
I would not go so far as to say they are more common than bottom drilled overflows but they are pretty common.