Overflow and return

[bnagy0]

I have a 135 gallon glass tank with 3 holes drilled 1.75". The holes are located on the back panel, 1 in each corner and 1 in the center. Holes are about 4 in from the top of the tank.

My question is, which hole(s) should I use as my overflow and return?

Or should I use all 3 as overflow lines and put in hang on back returns?

 

[RocketEngineer]

I would use all three to set up a BeanAnimal Drain Setup and go over the top of the tank with the returns. If all three holes are at the same height, it would be very easy to silicone two pieces of glass to the back of the tank to form the overflow box.

HTH,

 

[bnagy0]

Thanks, that is a great design! I m going to build it asap.