Your Bichir is not one that I had generally seen in the aquarium trade very often. I've only encountered them a few times. Bichirs do have many same similarities however. It is good that you are keeping your young specimens in a holding or quarantine aquarium to watch them. Almost all Bichirs are gathered from the wild and require some time to get used to the riggers of captivity. Some of things that all Bichers have in common is that they use their sense of smell over sight.
Some of the foods you mentioned should normally be consumed under wild conditions, but in captivity, that may require not only a meaty-type food, but actual assistance on your part on the way the food is present or made available to them. If you have a light over their tank, I would turn it off and just use ambient room light. But I digress. The way my husband and I conditioned new young Bichirs was to use very long stainless steel tweezers. We started with thawed frozen bloodworms and had to literally hold the worm(s) in -place just ahead of them. We then graduated to tiny thawed frozen clams and did the same thing. By the time the fish reached abut 6 total inches length, I would alternate holding the food in front of them and releasing it in front of them. They eventually must have learned than they actually had to spend some energy going after the food themselves. It varies on the learning for carnivore sinking tablets, but eventually those would work also.
So, I guess it is not only what you feed them, but how you feed them. Those long tweezers worked very well for us.
I almost forgot something.....You should be providing some kind of cover for yor fish to duck in and out from when they start actually search for food and while they are being observed and conditioned in quarantine.