The tadpoles are alive and well in the tank, as are all of my other fish in aquariums. I've never had any problems with the water quality. We get good, fresh, water here and use it to fill up our pond which is often home to wild frogs and toads, along with eggs and tadpoles/froglets who all survive and do fine in our water. I don't know :/ but he died with his mouth open, and I might have just been imagining it but his head and throat kinda seemed larger. I tried to open his mouth a bit but it was too hard to tell because hes so tiny.