I've recently been turned to using food grade whole frozen smelt. Cheaper then buying frozen silversides. They are individually frozen so no big block of fish. They're made for human consumption so they are really clean. No smell or mess. My Ray and other piscavores had no problem switching.
it's not a problem but it's probably a better choice to feed/buy tilapia and etc by the pounds from your local wholesaler or walmart & etc
as these are cheaper and cleaner to feed. not to mention you can cut these filets to any size you want or even mince them for smaller fish
or fry.
I'm favor with frozen smelt, its easy to feed my fish and smelt come with different sizes, there are 3 sizes (fish size) bag in my area S/M/L.
Size small content under 2 inches smelt, Medium come with 2~3 inches smelt, and Large with 4~5 inches smelt.