well mice are very easy and cheap to breed so that could be a saver. but im not so sure on how good they would be for a ray. since rays diets have alot of fish in them going to a mammal diet might not be the best bet since nutritionally they are very different. but i could be wrong.
am guessing one time might not hurt? where do rays orrginate from? maybe in their wild habitats occaisonaly a rodent will fall in there river and might be gobbled up by a ray. get it on video as i cant have fw rays =[
You don't think a mouse, rat, or other mammal has ever fallen into the amazon and gotten eaten? Granted it's not a staple for fish, but it happens. I've caught brown trout with flies that imitate mice. They didn't hit because they've never eaten a mouse before.
Not saying it a good idea to feed pinkies everyday, just dissagreeing with the total exclusion of your statement