dead pond goldfish

Question
For the second time in three months, I have lost all of our pond fish quite suddenly.
It seems to happen after a few days of rain.  My thoughts so far include:
:Can rain be the reason?  Can something get washed into the pond that poisens them?
:Can the increased frog egg activity affect them?
They seem quite happy and keep the pond very clean.
Any ideas?  

Answer
Hi Trudy!
Sorry to hear about your fish!
If it always happens after a rain then you are right to suspect that something is getting washed into the pond.
Examine the area around the pond very closely. Fertilizer, insecticides, and other stuff we use around the garden are all very harmful to fish.
Also, if treated lumber is used anywhere near the pond it can contribute to poisoning the water (treated lumber contains all kinds of poisons including arsenic).
Brigitte