Hi I have about 12 Koi and gold fish they are 1 1/2 years old and some are just from this year. I have been able to only let the rain water fill my pond until recently and it's getting a little low due to the hot weather. I live right by the River and would prefer natural water if possible. I used tap water last year and it killed a few of my koi as I was new to being a koi owner I did add quick fix but some of them still didn't make it. Does anyone know if the water from the river would be ok for the pond I would only add a little at a time. What do you think?