Actually, silversides AREN'T a good basic diet for snowflakes, as they are specialized crustacean feeders with even their teeth modified for crushing....you'll find that on a diet of raw shrimp and squid or octopus (available in many Greek or Japanese specialty food stores) he'll do much better, and grow very nicely.
If you try the squid (cut into suitable sized pieces of course) be prepared for a reaction comparable to a feeding frenzy when you offer him his first piece.
Many to most SFE's will actually refuse fish if offered anything else, and once switched over to their normal diet actually become suitable as community fish.
We've had the one in the photo ( his name is "Lover"....it's Amore' **grin**) for almost 5 years and he's nearly 3' long.