I have recently gotten into fish breeding. I had to choose a set up and decided on 20 gal. high aquariums for my breeders. I have the water coming in over the top of these tanks, but 2/3 of the way up on the back wall I have drilled a hole to accommodate a ¾” pvc pipe thread bulkhead.
I want my tanks to be overflow style to help remove food and oils. I also wanted a very reliable overflow with an emergency drain. So here is how I set it up and if you like the idea they are simple to make. They may not be what you want for a display, but for a fish room they are easy to make and reliable.
Here are the materials:

The 2” coupling is slotted 1 ½ in deep with a table saw and then the mesh is glued over the top.
This example is of a frag tank, bur it shows the overflow in profile:

I want my tanks to be overflow style to help remove food and oils. I also wanted a very reliable overflow with an emergency drain. So here is how I set it up and if you like the idea they are simple to make. They may not be what you want for a display, but for a fish room they are easy to make and reliable.
Here are the materials:

The 2” coupling is slotted 1 ½ in deep with a table saw and then the mesh is glued over the top.
This example is of a frag tank, bur it shows the overflow in profile:


