Size of Food for Anenome

[robreef]

I have a couple of BTAs in good health and 4 inches wide and I usually feed them bits of squid once a week, however I thought I might try silversides. I gave them each a whole silverside (which in hindsight I should have cut in half) which were thin but about 3 inches long. They engulfed them in their mouths but seem to be struggling to eat them. The anenomes seem to be regurgitating the silversides and then swallowing them again. The silversides even look partially digested when they come up, but the anenomes don't let them go. It looks like the anenomes are winning the battle.

Is this normal for anenomes? Will they be harmed if given pieces of food too large?