Hmm, how interesting... My dwarf is very alert. Everytime something goes into the tank he would quickly investigate, and determine if it's food.
Once my friend used my tank as a holding bay for its clowns and damsels (still in the plastic bag of course). Immediately the dwarf came to check. Within minutes, it started to "attack" the LS. Even though the clowns and damsels are bagged, they still jumped as if on fire.