I drop in (one at a time) roaches, crickets, wax or butter worms and watch to see who is eating what. I try not to leave anything in the tank so I can monitor who is eating what but then I feel sorry for them and will leave a couple of crickets or roaches in the tank. Since the calcium or vitamins wear off it kinda defeats the purpose of dusting them. They use to eat non stop with the tweezers about a month ago then just stopped taking from them. For awhile I was afraid they were over eating and both were getting really fat, but I still offered food until they turned away. They are both really active at night, just not eager to eat like before.