How long have you had the LTA?
What are your water parameters -- with numbers
What lights do you have?
What size tank? (( how long has it been set up ))
Even though I hate using silversides, a healthy anemone should grab onto it right away -- or any food for that matter -- if it isn't something is off.
I no long have any LTAs (( just 4 S. haddonis now )), I would feed them about once a month -- frozen/thawed krill.