I've heard filefish will graze on aiptasia. A copperband butterfly is more often the go to choice for an aiptasia eating fish, but they can be tough to keep alive, especially if they are successful at reducing the aiptasia.
I had a copperband who would come eat aiptasia off frag bases I would hold in my hand.
At one point I had a truly severe whole tank infestation and was able to eliminate it entirely using berghia nudibranchs. They are way more thorough than fish and will eat every single last bit of aiptasia until it's all gone gone gone. Fish will eat / rip off most of the nem but a small amount often remains at the base which of course then regenerates.
It took a couple months for the berghia population to multiply, but then the aiptasia just started to vanish. It was awesome.
If you only have a few (not enough to support a breeding population of berghia), the best approach would be to use Aiptasia-X yourself.