External overflow questions

[constantne]

So I took apart a 40G breeder and had the pieces cut and beveled. I plan on making a 25g rimless tank, much like a 20G long just a bit deeper from front to back. I want an external overflow but dont know anything about overflows. I attached two pictures of my ideas. What im worried about is having the tank crack on me from doing the idea in the first sketch.
What size external overflow would work? Can I do 1/4" holes leading to the overflow like the second sketch? Would they have to be totally submerged?
Also, if I were to do an internal overflow, what size can I do and do I drill the back or bottom glass pane?

 

[natclanwy]

I would go with an internal overflow for sure, your idea with drilling 1/4" holes would work as well but I would be worried about critters or other large piece of debri getting caught in the small holes and causing a flood. I have seen a tank setup with an overflow similar to that but the glass/acrylic (not sure which it was) in the back was notched instead of drilled to create an overflow.
Whether to drill the back or the front depends on how you plan to set it up and your stand. If your sump will be under your stand and you can run the plumbing through your stand drilling the bottom would be the best solution as long as your bottom pane isn't tempered. If your sump isn't going to be under the stand or you can't run the plumbing through the stand drill the back close to the bottom.
You can probably do whatever size you would like the gph are determind by the size of hole you drill a 1" bulkhead is aprx 600gph.

 

[constantne]

Thanks for the quick reply!
Maybe if I had enough holes it would be similar to overflow teeth. I just dont know if they should be fully submerged or not. I just hate the look of an internal overflow but its still something I need to think about.
I could definately drill the bottom since its not tempered and im making a stand. I would just worry about drilling a hole pretty close to the edge of the pane.
I was planning on an 1" drain I just wasnt sure how big the overflow box had to be. My concern is how would I get a fish or anything that gets back there out.