No, at least i have never heard of that, nor do i think it will work. Also brine has almost no nutritional value, its like candy for fish, dried food isnt much better. I would switch to a variety of different frozen foods.
Unless you see him eat the food, i would assume he is only eating live foods. Also for further reference, never buy a fish you dont see eat in the store. Its a good indicator of health and it can be very hard to train a fish to eat our prepared food. Its awful to watch something to starve to death. Also never trust a lfs employee 100%, you have no idea if they even have a tank, if they have taken care of it properly and there whole job is to sell you something. If it dies and you go back and buy more, that is better for their bottom line.