Vary the fishes diet as much as you can. There's no reason why you can't switch to the pellets (which, yes, are healthier provided they have enough protein) and supplement with live food every once in a while. Also remember that the fish won't be able to eat ghost shrimp forever. Once they're big enough, they won't even notice them.
Personally, I feed market shrimp. I have to deshell and detail it myself, but I don't mind. My fish love it and I get excellent coloration and growth rates from it. I supplement that with chopped earthworm (you could consider it diced for the babies lol), the occasional silverside, and sinking Massivore pellets.
I think if you check Beblondie's sticky (the primer one) it'll tell you the breakdown of nutritional needs you need to look for in bichir food - complete analysis of the percentage of protein versus the yata yata and even what the vitamins will do. It's an excellent read if you haven't done so yet.
Keeper