Setting up Frag tank

Hi all - I am setting up a new system and am trying to think a little ahead. I will be putting my sump / Refugium in the basement -In the room (its a large room) I also want to set up a frag tank - I have plenty of flow from my sump and already built in a line with a ball valve to direct water to the frag tank.

I picked up a 40 breeder from petco (on sale $1 a gallon to end of month I believe) its little larger than I wanted but is not as deep as the other tanks they had.

Okay - so I have some black eggcrate to build up a platform - I have a light and a powerhead - but what else do I want to put in it?

I have some rubble live rock not using in the DT I was going to put in the sump - but also could get some more for the frag tank if recommended? I assume it would be under the eggcrate as I will build this up about 8" from the bottom.

Also what about a fish? I see some In my LFS sometimes in there frag tanks - I there a better fish to use o recommended?

Thanks for any input - I really want to set this up the right way.