Just like you, we have tried everything at one point or another. I agree that the filefish eventually will pick on corals even though they do a good job with aiptasia. Berghias can be good if you have a fish less system, and also if they do wipe your aiptasia, they will just die off as they don't eat anything else. Not to mention they are expensive snacks. We have had good luck with peppermints in our frag tank, they keep it pretty clean, but they will not really go to town on larger ones. The copperband in our display keep is 100% clear. He gets everything and it a great fish. We have not tried a kliens but good to know, I have also heard a marginalis is an amazing aiptasia eater but they only come in rarely and are very expensive compared to the other two. I will be curious to see how the new reef zapper thing they had on Reef Builders will do, expensive but if it works as explained, could be a game changer.