Thank you for your input! Would you mind giving me a link to the sources you use? All the research I have done says a single D. auratus would be fine in the floorspace that is provided in my setup. I don't know yet whether I'll be getting the crabs instead of a frog, or putting them together, but I know people do keep them together. I think maybe you don't know what a vampire crab is?
If you'll take a moment to read my initial post, I did say that while I have not had a frog, I have had exotic animals such as spiders and scorpions. I have plenty of experience raising live food, including fruit flies.