Make sure it's not a pseudogramma gregoryi, as these are toxic/poisonous. This is the best image I could find.
I've heard that too, but I can't seem to find anything to corroborate that information - that’s not to say it’s not (and the OP should definitely treat it as if it is toxic), just that I haven’t found any confirmation it is. On the other hand, they have confirmed
Pseudogramma polyacantha (a closely related species) is not toxic. There's speculation that the genus may not be toxic at all, and they may just be thought to be toxic as a result of their arguably somewhat inaccurate taxonomic classifications.
Again, though, OP, as we don’t know for sure one way or another: please be careful handling the fish, and - if it is toxic, it would probably be toxic in the same way soapfish are (grammistin is the toxin name - it’s an ichthyotoxin, so it’s primarily effective against fish, but it
is effective against humans too [it causes mammalian blood vessels to rupture]), so if it gets stressed it would likely release more and potentially kill your other fish.
From what I can tell,
P. gregoryi and
P. guineensis are the most likely species of this fish, but there are a couple other species in the genus that it could be as well (particularly if it’s still a juvenile). To my knowledge,
P. gregoryi is the only one considered to be toxic at this time, but others may be as well - to reiterate we don’t know for sure at this point for any species but
P. polyacantha.
My source:
