Setting up a display refugium

[esimplx]

Good afternoon! I have a 125g display with a 100g basement sump (stock tank). I want to add a large refugium as a source of pods, nutrient export, and pH buffer. I picked up a rimless 50g tank that I want to set up as a combination macro algae display and fuge. The lighting cycle would be reverse of the main tank.
First I can't decide if I should go with sand, mud, or bare bottom. I'm worried the decreased number of detritovours compared the main display may cause iddues.
Second, cuc? I want to keep it simple but also want the tank look well cared for. In the main I have a foxface and a urchin that keep things tidy, but that won't work in a fuge.
Let me know your thoughts, I would love to see what other have done to make a "display refugium"!

 

[esimplx]

A few pictures of the setup. Tank is still a work in progress, especially on the coral front, but everything is happy so far.
2 clowns
3 blue chromis
1 one spot foxface
Long spine urchin
Lot of various cuc and inverts including a pistol shrimp, a conch, a few starfish ect

 

[zaphod42]

I know this is a couple of months old, but did you end up setting up a display refugium? How's it working out for you? Pictures?