A varied diet is best,

When I kept ACF's I fed a rotating mixture of frozen (not freeze dried) blood worms and krill shrimp as a treat.
A staple of TetraFauna ReptoMin Sinking Granules Aquatic Frog & Newt Food. When they were small 1in STV
and Reptomin Plus when they got larger.

Also for treats I would feed 1/2 of a night crawler to each adult by hand ( they loved this)

What would do to slowly wean off the salmon pellets is to feed a few salmon pellets and get the little guy
in a little bit of a feeding frenzy and drop in a pellet of the reptomin plus and see if he will eat it.

Good luck!!

I miss my ACF's