Mandarins are actually not tough to keep if you have a large amount of live rocks with pods living on them.
If they are in your established 120, I would not worry about your mandarin with or without refugium. My pair in my 120 have been fat and happy for about 3 years now, spawning pretty regularly. I noticed that my 5 yellow tail damsels are also eating pods a lot (they go nuts on tiggerpods and bbs), but their consumption does not seem to make much difference to the way my mandarins look and behave.
I hope your pair will soon start doing their courtship dance. They are so beautiful swimming side by side.
Tomoko