I need a backup staple

I have two issues with earthworms: one of my axolotls doesn’t like them much, so he never eats quite enough, and I have a hard time sourcing them at this time of year - fishing season is over, ice fishing hasn’t started yet, and online stores don’t want to ship due to the weather.

I’ve been raising red wigglers as an alternative food source, but one of my lotls (the one who likes earthworms) always throws up after eating them. She also throws up frozen brine shrimp.

I’ve tried Repashy’s Grub Pie, but they prefer smelling it than eating it.

I’ve tried sinking trout pellets - they won’t touch them.

At the moment they’re mainly eating frozen bloodworms, which is problematic both for their health and for my wallet. They would eat fish culls, but I don’t have any right now - all my fish are looking good. I could spare a few guppies, but I’m hesitant to feed them perfectly good fish - I’d rather feed them something that can’t feel pain, you know?

I thought about switching my red wigglers for black fly larvae, but I’m seeing conflicting reviews about their use as amphibian chow.

Any suggestions based on your personal experience?

I’m updating this in case it can be useful to somebody: both of my axolotls readily took to the black soldier fly larvae. They have been stuffing their little faces! I can happily say that my fussy male isn’t underweight anymore. I’m going to be alternating between earthworms and BSFL from now on. I love how easy the BSFL are to care for. Plus, they eat all the food waste red wigglers dont eat, and vice versa, so together they really make the best composting team! The only downside to using them is that it takes longer for my axolotls to catch them all, whereas worms are faster.