While most cowries are omnivores, it is accepted in the hobby that the Money Cowrie is an herbivore.
The Tiger Cowrie prefers a rock aquarium with hiding places. While small, it will eat some algae and scavenge for scraps, but as an adult, it will eat some anemones, sponges, and soft corals, and is best housed with starfish, sea urchins, and tubeworms in the reef aquarium.
My guess is you got a Tiger?Dude at Petco said they may start eating softies, so I'll have to keep an eye on that.