If anyone owns a pet goldfish, aquatic snail, shrimp, or hermit crabs here is a little info on something that's toxic to all of them: copper sulfate.
Copper sulfate is found in all fish food, and is highly toxic to snails, shrimp, and hermit crabs. It is toxic to certain fish species as well including goldfish, trout, and koi. Studies have shown it kills them and takes up to 30 days for them to heal from the effects if they lived.
Fish food companies don't seem to care about our aquatic pets at all. On top of that, goldfish need a high veggie, low protein diet because of their digestive system. What do fish food companies give you? Low to no veggie, high protein. A high protein diet can cause swim bladder disease in goldfish which is essentially trapped gas that makes it so they can breathe and eventually their body shuts down.