Hi,
are the red ones (so called) Dendrobenas? If yes, they are perfectly fine. You are right about the mucous, but the frogs seem to get kind of used to it- mine voraciously eat Dendrobenas on a regular basis, but they have grown to be somewhat hesitant about Lumbricus (i.e. nightcrawlers) of the same sizeOther frogs refuse to eat Dendrobenas- seems to be a matter of taste. I think both species are worth a try, at least none of them will harm your frogs. Also, I wouldn´t be afraid of deterring ACFs from eating- well, anything. Even if they don´t like the red wigglers, they will forget about it soon and still try to eat other worms.