I know you dont want to hear, maybe you wont even believe me, but these guys do not live very long eating a dead only diet. To successfully keep them long term on a dead only diet you will need to get them to not only eat silversides for the bones and guts, but also fresh shrimp with shells. They will also need fatty fish like tuna and salmon with the skin on, fresh preferred. This is what they will need nutritionally, and thats a tall order, because most of them are picky eaters. Even if they take to dead food, its usually short lived, going on hunger strikes frequently, and not really eating enough, just taking a chunk here or there as a feeding response.
Hikara silversides is what I recommend, they are a variety of fish which does not contain thiaminzse, which binds vitamin B1. There are other food choices but these are the ones I know of, supplementation may help, although I still don't know anyone keeping these guys much more than a year on a dead only diet, usually much less. Vitamin defiencencies can take hold in just a few months, I've known a few that only lived 4 or 5 months eating only silversides.
You should get them off rosies, these contain high amounts of thiaminese and they have a hard time digesting them, which can lead to bloat.
I feed my rhino mollies, some Hikari silversides, and some fresh shrimp. He mostly eats live I have had him for about 2 years.
It is better to feed them smaller items rather than something too large, especially a dead food item. I would cut a 3" silverside in half. Maintaining reef levels of mg also helps with digestion. Overfeeding can also be an issue, a couple times a week seems to work well. They poop like a dog, so its easy to see if they are regular.
