Marie
You might have to venture out of the NORA section of reef central to get some better advice (no offense to the members here)--- you can drill holes in the back for returns or just run it over the top... add spray bars, etc....
For the size or number of the holes, really depends on the flow you want to run.... for holes in the back--- I would make a glass or acrlylic overflow box attached to the back of the tank (inside)--- there is a size calculator based on the flow you want to run on the home page of the site--- rather then run it to the bottom of the tank you will enclose the bulkhead(s) and add a dorso inside the box to quiet it down---
I post a help in designing thread in the lighting filtration and other equipment section or in Do It yourself-- I'm sure someone has done this before and you can pick their brain....
I'd decide on the flow you want to run for now then when you decide, ask for help in designing .... I personally like low flow (quiet and less bubble issues)--- I run less then 200 GPH through my sump from my 135 gallon tank... 3-5x tank volume is fairly popular but I know of some people that run massive flow through their sump---
You might even want to drill a couple holes for a closed loop too....
You might have to venture out of the NORA section of reef central to get some better advice (no offense to the members here)--- you can drill holes in the back for returns or just run it over the top... add spray bars, etc....
For the size or number of the holes, really depends on the flow you want to run.... for holes in the back--- I would make a glass or acrlylic overflow box attached to the back of the tank (inside)--- there is a size calculator based on the flow you want to run on the home page of the site--- rather then run it to the bottom of the tank you will enclose the bulkhead(s) and add a dorso inside the box to quiet it down---
I post a help in designing thread in the lighting filtration and other equipment section or in Do It yourself-- I'm sure someone has done this before and you can pick their brain....
I'd decide on the flow you want to run for now then when you decide, ask for help in designing .... I personally like low flow (quiet and less bubble issues)--- I run less then 200 GPH through my sump from my 135 gallon tank... 3-5x tank volume is fairly popular but I know of some people that run massive flow through their sump---
You might even want to drill a couple holes for a closed loop too....