Yeah pop the lid on the night crawlers before you buy them, I've had a few trashy ones where most of them looked almost dead. I'm not going to feed mine a f/t mouse until he's about 8 months to a year old probably. I'm not crazy about feeding frogs rodents, especially for their health. Obviously when I do feed him them it will only be one every 1-2 months. Starting with 100 dubias adult you should be able to pick out of it heavily in 3-4 months, that's the only downside... If you got extra males though that eat up your food or fight the other males definitely feed them off as George suggested. 1:10 ratio male to female, they can impregnate a lot of females. What's your setup like for the dubias you're probably getting tomorrow, what heat source?