20g Refugium DIY

I know a million of these threads have been posted but i read some of them and just didn't get the info i needed. So here it is:
I have a tank that is about 30inx12inx13in and I am planning on making it into a refugium for my 125g tank. I already have a wet/dry (most of the bioballs are gone so don't worry) where im running my skimmer off of so i won't need a section for that. I also have a CA1800 pump (~635 gph). With that, I have a few questions:
1. Will a refugium this size be large enough for my DT, if its almost entirely a fuge (barring the return section). I have a 55g i could use if i had to.
2. Is this pump powerful enough, my fuge will sit next to the tank aprox. 2ft below the edge and have aprox. 5 feet for the water to travel across to the tank.
3. What size overflow would I need?
4. I want to set this up without drilling, is there a way to do that?
5. Anything I miss?

 

Yes, that will be a really nice size fuge.

Yes, you want fairly low flow through a fuge. Make sure you put a ball valve on the pump though to be sure your overflows can keep up.

Because fuges need such low flow, I would just T off your existing overflow plumbing to run to the fuge. Be sure to put a ball valve in the line to fuge after the T, so you can tune back flow.

Yes, you can either T off your existing overflow like I mentioned or use an HOB overflow.

It sounds like you are on the right track so far.

 

Sounds good but sounds like you have the choice and room so I'd go with the 55 (partitioned). With that size fuge you shouldn't have to worry about nitrates and phosphates if it's done right.

 

If I had to i could use the 55g, but id prefer not to. Will i get enough advantage from it to warrant transfering all the fish in it currently (freshwater tank) into a different tank, cleaning it out and paying for sand, lighting, etc.?

 

You mentioned something about having a wet/dry. I'm not sure how much room you have but if you have enough for a 55, I would partion the 55. If you have an in-sump skimmer I would partion it for a skimmer/return/fuge and get rid of all the other smaller tanks. Less room for error/flood, no need to drill anything, etc.....nice, clean setup.....just what I would do, I'm sure not all would agree, so it's pretty much your preference...both will work.