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It’s a very pretty image, I like how low you went to help the blenny stand out from the reef, and the vertical frame suits the subject well.
I too wish the top horn/filament wasn’t cut, but nothing stops you from “trimming” the very top of that filament in your favourite editing software (in Lightroom Classic, the “remove” tool does wonder on scenarios like these).
I don’t find the background too distracting because it is well out of focus, but I’d recommend always check what the background is doing for/against your subject, and possibly rotate slightly around the subject, to get a different background.
Final editing touch I would do: darken slightly the dorsal fin, which is eye-catching and tends to drive my eye away from the picture.