my initial recation is that it seems so cruel, but to answer your question, they are very small when first born and normally hang about the rocks hardly moving. at this stage they are vunerable and frequently get eaten by larger fish, however i cannot reccomend that you use them as a pimary food source for your larger fry. as i have never heard or read a recommendation to fo so from anyone in the fish trade, also there are purposefuuly produced products to feed young fry which may offer more balanced nutrition such as liquifry and first bites.