After looking at the similar post, I came up with the same question. Is this a beaugregory or a cocoa damselfish, and how can we tell?
I'm going to say it is a Cocoa Damselfish because the dorsal fin spot appears to be on both the dorsal fin and the body. The Beaugregory dorsal fin spot is only on the dorsal fin and doesn't run on to the body area. It also looks to have the little black spot (of "cocoa") on the tail base, which means it's a Cocoa Damselfish. (That's how I remember).
Just a snorkeler-Island Barb
Perfect answer. Granted the differences are very subtle, but you clearly stated them and fully answered the question. Brava!
I am selecting, copying and pasting your explanation to keep for when I (inevitably) forget.
REEF Headquarters | P.O. Box 246 | 98300 Overseas Hwy | Key Largo, FL 33037 | USA Phone: 305-852-0030 | Fax: 305-852-0301 | email: email@example.com