Btw, i have used fresh lemon juice to inject into aiptasia and it works. Once you inject them using a syringe directly, they will die within a few mins to an hour depending on how big they are. Just buy a fresh lemon and use about 30ml to 50ml depending on size. Its effectiveness is 10/10. But remember to increase your pH after getting rid of these pests as lemon juice will decrease your pH.
This tip is from reef central.
For those newbies.
Aiptasia are considered pests in the marine aquarium hobby, because they are stressful to coral around them, and occasionally even sting fish. They are often accidentally imported along with live rock. Once present in the aquarium they are notoriously difficult to remove as attempts to remove often inadvertently create more.