You could put one back there until he eliminated the issue, then net him out and put him in the DT.
+1^^...i was very lucky to have added only 1 peppermint shrimp and he must have been the aiptasia eating version. He ate the only ones i've ever had (so far, knock on wood :fingerx and then my cbs killed him
i took the cbs back to the lfs as soon as i could get him caught out.
I would not hesitate to get another peppermint shrimp if i had aiptasia troubles.
*Coral Banded Shrimp ....aka: little creep that terrorizes after the lights go out (IMO)
I had aiptasia in my DT and fuge, a peppermint shrimp in each solved that problem quickly.