Blaso or Acan?

Here is my Blasto or Acan. I'm not sure which and its difficult to identify in books. The local fish shop said it was a Blasto but a friend who has kept marine fish for years reckons an Acan. Any experts out there? It looks like an alien something anyway especially when the blue light comes on. It iridesces which has a hypnotic effect. It is really an animal and scoffs up live food as it has stinging tentacles to immobilise its prey then conveys it to its mouth. Its amazing and very beautiful in a brutal kind of way.