Jpsdad, you may want to move me to your right shoulder. The vast majority of aquatic environments in the U.S. contaminated with "Mercury and other toxins" , are contaminated via atmospheric deposition. Have a watershed that feeds your pond?
Your pond, if you use copper based algaecide, is more contaminated with forever chemicals than natural bodies of water in your area. It will be an EPA superfund site one day.
If you eat fish fed from commercially available manufacturers, you may as well season them with aspartame and arsenic then fry them in formaldehyde.
What is in your fish food? Manufacturers know the secret of making fish food. Fish who die, don't have relatives that lawyer up. The protein percentage of your fish food is a mathematical calculation of the nitrogen and to a lesser extent, phosphorous content. How do manufactures "sometimes" increase nitrogen, thus protein percentage? Usually melamine and cyanuric acid. What else is in your fish food? No one knows but your pond water.
Adding nitrogen and phosphorous to your Mercury and copper pit assures future generations will never enjoy that body of water.
You're outdated with your melamine and cyanuric acid comment, but when it was still happening it was more common in ag and pet foods. Season your pork chops the same way I guess.
