Gonna throw my tank in the truck tomorrow and take it to a glass shop ...

If it can be drilled, I want to have it done so I can install an overflow (or overflows) before I get too far along.

Question: how big a hole (or holes) and in what location?

Tank is a 75 gallon. I lean toward two overflows, one in each back corner, but I'm open to suggestions.

Thanks!!

 

Put in a couple extra holes and plug them. Then if you want to add something later it is no big deal!

 

Sounds good to me!

What size holes though, and where?

 

+1 Wish I woulda done it on my plywood tank so I could go with closed loop later... dang Dual overflows is a great Idea. Do some research on how much gravitational flow you can get through a certain diameter hole. Then pick your size based on what you think might one day down the road be the absolute maximum sized pump you will use.

 

This place has good info about this stuff. I got a kit for my 20G tank and it worked out great!
Glass-Holes.com dope aquarium stuff : Home

 

To add to this, it's better to go larger to be on the safe side, as you don't have to push the water to the OF's max rating, you can always go less. For a 75G tank, I would think a couple 1.5" bulkheads would be good. That would be somewhere in the 1200GPH range, given proper plumbing is done.

 

I would say the bottom would be most convenient.

 

Average 1" bulkhead requires atleast 1.3/4 hole and it is tight 1.13/16 to 1.7/8 will allow some wiggle room . Just buy a good bit and drill it yourself most local shops charge 25.00 ea. to drill a hole..

 

Make sure you take into account holes for closed loop system! The thing I regret the most about my tank is not doing enough holes.

 

Too true... I would do 4 or 5 extras.