Lawnmower Blenny

[Delphinus]

Have you tried nori (I know you said seaweed but that could be a number of different things). If memory serves, they are a scraper of film algae, and it's only chance if they take to other things like filamentous algae (not guaranteed) or prepared foods (also not guaranteed, like you've noticed). So nori might be a good bet if you haven't tried it because it's soft and might be the texture he's looking for. But don't just offer it loose or in a clip: roll it up around a 1/2" PVC tube so that he can "scrape" it off. Or try a small rock to make it more natural but I've never been able to get nori onto a rock very well, a smooth surface like PVC is better IMO.

IIRC mine did not take to prepared foods until well after a year. Then he went nutso for food (mysis in particular) and looked like he was about to pop. He lived around 4 years for me, towards the end he just stopped eating again, got thin and eventually disappeared. I have no idea what their natural lifespan is, 4 years might be average or it might be terrible compared to what it ought to be.

Good luck.