0 Pets

I have no idea what happened. On Sunday I decided it had been one week with our pets and they needed fresh clean water. We carefully scooped out the tadpoles, still had 13 good swimmers. Changed out the water and put them all back in. I pre-treated the water with the special drops just like last time. The only thing we did different is added a Lilly bulb and not line the bottom with sand. This morning they were fine when we checked and by 2:00 pm all dead. I can't figure it out. The kids were not as sad as thought, they just said "Can we go get more?"