Hey I recently got a fluval 305 canister filter used. It was used on a saltwater tank so it has a bunch of little crustaceans or whatever you want to call them inside the filter. I tried to scrape off as many as I could. They are just like little small white dots everywhere. See the pic. I have washed all the media thoroughly and it cleaned up pretty well. But I was wondering if I could still use it on the freshwater tank or the little speck things would hurt the fish. Thanks
It is probably just calcium deposits.
Should cause no problem but may raise your pH(doesn't matter) and GH(matters more).
Set it up and get a good test kit to be sure.