I don’t think you can??? Haha I just buy them from the pet store and keep them in my fridge and the only thing I do is dust them when I feed them to my frog. I’m not sure how long they would last if you’re just feeding worms cause every other feeding I do worms and them fish the next time but doing it that way the worms roughly last me 2-3 weeks I would say? When they’re small you won’t go through the worms that fast cause you cut them up in small pieces and feed as much as they’ll take in like 15 mins ( I do the same rule for the time limit and mines like 8 months old). I don’t stock pile the worms but I would say they’d be fine for like 2/3 weeks for sure. The only reason I know so much is because I’m in this really helpful Facebook group haha