Acan thoughts

[Big B]

It looks like the center of this single acan melted or was eaten by something. Anyone ever see something similar?
Current tank members are a couple peppermint shrimp, cleaner shrimp, emerald crab, yellow tang, hawkfish, two clowns, midas bleeny and a royal gamma.
Water is sitting at
79 degrees
1.025
5 nitrates
.04 phos
430 cal
7.8 alk
1300 mag

 

[Tahoe61]

My bets are on the shrimp, specifically the peppermint shrimp. The Acan probably had digested some food that the shrimp wanted, but it could also be the emerald.

 

[Big B]

I wondered, they are suppose to be eating the aptaisia.