Silversides are Not a good food source long term; elegance can take food bits that big, but have difficulty digesting all the bone and such. Usually ends up wasting most of the food. Frequent feedings with much smaller food sources will serve it better long term; you can use fish filet, shell-off shrimp, mussels, etc, just think mysis shrimp sized bits when you go to feed it.
That is a beautiful specimin bad habit; how long have you had it now?