I'd very cautious with this. Like Deb mentioned, toads can carry crypto. And in all honesty I don't trust the water at many local pet stores. I've been in the aquarium game for many years and have learned to avoid the water from the stores. I stopped buying feeder fish and started using a quarantine tank before introducing new fish into my main tank(s). I just had too many battles with fish getting sick. Once I took the pet store water out of the equation I no longer had any sick fish.
Also, when I got my Hognose boy a few years ago he wasn't eating. He had apparently eaten once in almost a year before coming to me. I followed Deb's advice to a T and have had no problems with Cosmo eating ever since. Follow Deb's advice, she knows her stuff.