A Coral Beauty will be fine provided that it'll be the very last fish you'll be adding.
I've got the Fish-Saver from inTank, it works like a charm! I had a Midas Blenny that liked to hop in to the overflow, and it's a PITA to get it out with the media basket, skimmer, pumps, heater, etc.
I'd also suggest a good skimmer, this is the one thing that you should not cheap out on. I've gone through 3 skimmers because I didn't want to bite the bullet on the Tunze 9002 Nano DOC Skimmer. Now, I see it as one of my better investments.
Cutting out the section between Chambers 1 and 2 is a really easy way to increase flow into the overflow also.
The BioCube is a great first tank, expecially if you like to tinker and mod.
