Adding livestock to solve a problem isn't normally a good way of addressing an issue. Along with that, it is highly hit or miss if a peppermint shrimp, as they are the only ones known to go after aiptasia, will even eat aiptasia at all. Get some aiptasia-x or joe's juice and nuke them. Highly effective. Could even try shooting boiling water/lemon juice into the aiptasia's mouth.