Q.Are pecan parts poisonous?
I have a small (75 gal) fish tank in the backyard right under a pecan tree. When pecans drop in it I am able to fish them out daily because they float. But the squirrels have been very busy chewing on the pecans and the parts fall into the tank and sink. This morning I pulled out about seven dead fish and I noticed the water looks very brackish. I imagine the rest of the fish will die as there is no way I can keep up with the squirrels. Am I right? Is it the pecan parts that are killing them?

I didn't find Pecans listed as toxic to fish, but I would check with an expert in fish. This is outside of my expertise.