As feeders?? Lol jk. I'm no expert by any stretch. But I would think seeing as how the silver will seriously outgrow the discus there's probably a good chance he would eat them. But then again some people I've seen do keep aros with smaller fish with out much incident. So I imagine you'd have to monitor that and see what happens
I have a 32" silver with a 4" silver dollar and some larger red hooks for almost a year and they have never been touched. My asian aro likes to chase them though lol