Fish Stocking Question

[molotov]

My display tank is 165Gal. I have a pair of clown fish, three pajama cardinals and a blue hippo tang.

I quarantine all my fish for six weeks before introducing them into the display. I would like me next fish to be a Copperband Butterfly for sure.

I have a 15Gal quarantine tank that I will use to hold the fish for six weeks. My question is this, what other fish possibly two in addition to the Copperband would you have in a 15Gal Quarantine for six weeks. I understand the Copperband is quite a fragile fish and they tend to die quite easily. So I'm looking for a low stress fish to accompany the Copperband.