Wondering, whats the best type of worm (both in nutrition/safety and cost)... I usually feed my large SAs frozen blood worms, but they are low in nutrition, small is size and high is cost considering how many cubes i need to use at 1 time ...
Depending on the size of the fish, anything from small baby earth worms to night crawlers. You can cultavate your own, so cost once established will be very low. You can start off with some Red wigglers from the bait shop or PetSmart.
Earthworms and nightcrawlers are (in my experience) a heck of a lot harder to culture than red wigglers. I just have a bin in my garage that I use as a receptacle for any kitchen veggie/fruit/paper waste.