Just a little more info. Since they had been in that water and were so healthy, and knew they needed the algae to eat, I figured natural was best and kept it with them and just slowly added tap water that I left out and added fish tank dechlorinator to. I also did it in an airating way just in case. I put a piece of cardboard over 3/4 of the top so they had sun and shade. It was also in a spot on my porch that had direct sun half of the day but surrounded by shrubbery so it seemed like a perfect mix of sun and shade. Also had an empty plastic pot in the middle which had a nice gradual, grippy but not rough incline to bask on or hide in and put some plants that the adult tree frogs around the house like inside for roots and stalks to rest in underwater and above. This may have been my mistake as I can't know for sure they weren't toxic. I thought they were a good bet but I guess I was wrong. The whole thing seemed like a pretty perfect recreation of a pond and they used every bit of it, seemed really happy. Also fed them boiled and mashed broccoli and spinach although I never saw them eat it. I wondered if maybe it was the food since they died shortly after feeding. The whole thing broke my heart. I just really want to do right by the four that are left.