You can get some nice small sized BTA's for a decent price. Dr Mac and sons (www.drmaccorals.com
) was selling some BTA's for 30 bucks that would be perfect for your situation. If you called them and told them what you had they may hook you up with something that would work. If you take the carpet you could see if a local fish shop would trade you it for a BTA or at least some credit towards one.
I have a green carpet in my tank and when I got it the thing looked small but man when it inflates a whole different story. Plus carpet anemones would swallow up any small fish that got near them since they have a strong sting. Considering in a nano-set up you will want small fish I would seriously go with a different anemone and keep your friend's carpet just long enough to find it a suitable home.
Kudos btw on the nano setup. I looked at your pictures and I like how you did things with the CPR Fuge and BAK PAK skimmer, good thinking. I have a group called Reef Preservation and Coral Reef Aquariums on FaceBook. If your a FaceBook user you outta join and post some pics of that, I think the folks in the group would be interested to see it.