No, they know it's food, as I thoroughly defrost and mix with roe and pellets before I drop it in. They peck at it and then just let it drift to the corals. The silly, fat things are just like the rest of us -- they love their potato chips and cake.mix them together, they just don't realise frozen is food yet. Make sure the frozen is very small too, I grate some of bigger types of foods such as octopus and clams.