Is it a new setup? seems a very clean tank so thats the reason i ask. If so then watch your linka starfish as they dont do well in new tanks and need mature systems. And the boxing shrimp, be careful of this as the will corner and catch other shrimps and small fish and eat them.
I agree on the Linckia comment....stars don't do well in small/new systems. If that guy isn't looking well or dies, get him out of there as soon as you can. They disintegrate VERY QUICKLY. Otherwise, cool tank. SH