Yep the fangblenny is venomous.
Rearrange some rock work to make the dottyback think he's someplace else - new territory, he won't be so tough.
I've had less than stellar experience with the fangblennies - they often waste away, often getting them to eat is a problem. Was yours eating in the store? If so what did it eat?
Try
frozen mysis, that should stimulate a feeding response. Watch for him getting thin even though he may be eating... I think they're prone to intestinal worms (metronidazole is good for that).
Jenn
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