is this overflow?

hi,im a brand newbie,thinking of starting 40 gal fw tank,been doing plenty of reading on filtration and love the sump way but dont like top box overflow.can a hole be drilled at back of tank at just below water level to serve as overflow?how big should hole be?my sump will be a 14Gal tank.what size pump for return flow?sounds like a mouthfull but can u help me?THANX

 

You should be able to buy a pre-drilled tank or get a tank drilled at your LFS.

 

The size hole for the overflow will depend on the flow rate from your return pump. You can use valves to dial down both if needed. The amount of flow you'll want will depend on what fish/plants you want to keep.

 

Here is one with a built in over flow; 40 Gallon Aquarium|Rectangular Aquariums|Reef Ready Aquariums|Aquariums by Truvu

 

right, or your local glass shop/window shop.

 

This place sells kits for drilling your tank.
Glass-Holes.com dope aquarium stuff : Complete Overflow Kits

Also this place sells all the pieces separately.
Bulk Reef Supply - Bulk Reef Supply

They both have instructions and more info on how to go about doing it.