pepperment shrimp worked well for me. i dont think that your clarkii's will bother them either.
do you have a qt
setup? if so just put them in there for a couple of days without food and then let them go in the main tank. some say this makes them more agressive towards the aiptasia.
if not , i think they will solve the problem.my tank was overun with those things, atleast 75 of them in there.i bought 3 pepperments and put them in my 55 gallon and BAM!no more aiptasia. dorian