In the early days of freshwater ornamental fish breeding, one of the first mutations that consistently appeared in high profile species like angelfish and discus was a half black trait that originated at the tail. It seems like this mutation is not unique to fish from lakes and rivers as two examples of half black surgeonfish just hit our radar thanks to RVS Fishworld.
Coming from two different oceans the two half black tangs include one gem tang from Madagascar, and the other being a half black regal blue tang from Papua New Guinea. We’ve seen a decent number of unusual regal blue tangs, usually with some extra black coloration either being masked, nearly all black, or something in between so the half black regal tang follows a trend of aberration for Paracanthurus hepatus and is probably only the latest in more that will arise in the future.
The unusual Zebrasoma gemmatum with its round body outline really closely resembles the half black freshwater angelfish and discus from the middle of last century with even the tail being darker, but not completely black, and is one of the rare morphs of this really iconic west Indian Ocean species. It might not be a showstopping mutation but since gem tangs are very conservative in their appearance, only occasionally appearing with a bar code color pattern, it’s noteworthy to see an unusual example in a sea of this cookie-cutter species.