the thing is, to help these animals you are actually better to not give them any money or buy their pets. Because they make money from it, and they'll just order as many new rats as they sold from the exact same place and continue buisness.
I "saved" my rat from being snake food (she was a whoping 4.99 canadian dollars because she was in the feeder bin, because at that pet store black or black and white rats are feeders....) so I totally get you. I would have done the same thing, because it's too hard when you have a heart to leave them there... but the real way to make them take better care of them or stop selling them is to not give them any buisness and ESPECIALLY not buy their products, pet stores make the most profit off of the items in the store and not the animals which is why in general they don't take good care of them: it makes them lose time and money to take care of them properly.
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the pet store I was at we were 2, max 3 workers to take care of about 30 fish tanks, over a dozen reptiles, 4 bunnies, over 30 birds, 5-10 puppies, 10-15 cats and over 30 rodents. There is no way 2 people serving all the clients as well and re-stocking shelves can give proper care to all those animals.