I know I've read about diy diffusers for outputs using bottle caps secured to the output of canister filters to lower the flow for fish who can't handle high flow. that might help a bit if you put together something like that. I know coppers a big no no. I have no experience with pyrite, but I googled if pyrite was safe in aquariums, and I got a bunch of results saying it wasn't. Maybe try a vinegar test? I couldn't find exactly why its so dangerous.