It's not just any protein, it's indigestible protein you want to avoid. I feed NLS to all my fish and never a case of bloat.
Omega makes a good veggie pellet too, but haits are basically omnivores.
It is stress that causes most cases of bloat in the non-herbivores most of the time. Just give them everything they need: good water, plenty of room, and the presence of a bunch of smaller dither fish to improve their comfort level.