Well, for long term success they like a mature tank with very good water quality. I.E. low doc
, high circulation, aggressive skimming, stable parameters. These fish need some room, they constantly swim, grazing on algae on rocks and glass (they need a lot of this). They can also be difficult to get on prepared foods. Not an easy fish at all, and a 30g cube is pushing it. IMO
a 45g is the min for this fish, add to that you have a damsel in that small space with him and I think it spells trouble and stress. If you insist on getting one for your 30, you may consider taking back the damsel if aggression is seen (or return him 1st and avoid all together) and be sure to see him eat at the lfs
. Also consider a 45-55g in the near future if you want him to live stress free and have roaming room. It's the length of the tank that matters, not the gallons. That is where a cube tank falls short.
Honestly, I think something like a Maroon Clown or a pair of percs would be a much better match for that tank.