Best food you can feed your silver is pellets, get him started ASAP. Only problem with floating pellets is if your silver gets DE in both eyes, it cannot see the waters surface at close range so floating pellets are hard to retrieve.
My 9" RTG will not eat sticks. I've just got it on to prawn and I tried shoving a stick inside.
The sneeky fish spat it out, then retrived the prawn.
I'm going to fatten it up for a few weeks then i'll try starving it.