Pond Boss Forums INTRO Questions & Observations Should I drain it?

I am new at this and learning but I will give my 2 cents. I have a friend whom filled his pond from a creek. He filled it in early spring for several weeks. He ended up with all kinks of unwanted fish. When he went to refill when the pond went down rapidly he killed everything. The onlything I could figure was it was during the time the farmers were spraying fields. His creek has fields lined on both sides (very large fields). I don't know if that was what killed the fish but That was my guess. If it were me I would keep in mind of what actvity goes on up stream.