Hi i actually saw a documentary about the biggest leather poducers in india, and all the heavy metals and chemicals the use in the process, is shocking.
They collect most of it toxics burn it, and the goo that remains gets mixed with fish food and they feed their farmed fish with it.! This gets exported too freaks me out.
The viatnamese farming talapia etc, they have really no interest in eating their own fish, they are not that crazy far to much contaninants in it metals, herbicides, antibiotics, etc.
Avoid anything farmed is best for your health, and better for the enviroment, more even so for prawns that get farmed all this ""food"" is deadly.