postbeetle,
I doubt that you have been sabotaged...more likely a victim of overpromotion of fertilizer or other chemical usage. Something has caused excess nutrients to build up in your pond. Fertilizer is the first thing I think of, but it can be due to other sources such as a cattle operation that has drainage into your pond. Another possible contributing factor would be the numbers of fish in the pond..if there are too many fish, lots of nutrients are present and its dry with no otherwise provisioning of fresh water, that's a recipe for disaster.
If you do think you have been sabotaged, a water test might tell you what has really happened.
It must be a very sad thing to see, very sad indeed. Hope I never go through that.
