anemone care?

I first got my long tenticaled anemone, and asked the lady at petco what to feed. she refered me to MicroVert, a liquid food for invertebrate, filter feeders. I have learned that they also like meaty foods. I had a recipe to make some and he seemed to eat that pretty good. Since i first got him he has gotten smaller and now my clown and damsel fish eat the food before it gets to him.
Is there some nutritional factor that i am missing? What is the best food for him? Is there a feeding technique to ensure he receives the food?

please help
SEASTAR