Aiptasia in my tank - How to get rid of it?

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I just noticed one of these guys hitchhiked onto a frag I recently purchased. I heard that they cause issues in reef tanks with fish.

My problem is I can't seem to grab the thing because it shrinks in between a crevis in the rock before I can attempt to grab it. It also isn't very big. Any tips/ideas on capturing it?

It is on the left of the rock..small lil fella.
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