You can. Pool Stain Treat is safe for filter systems. We only recommend shutting off the pump if the pH is below 7.2. You can find more information in the Directions tab on the product page.
You sure do! While Pink Treat kills the pink slime and/or white water mold the filter traps it. Make sure to pay attention to filter pressure and backwash as necessary. If you're dealing with pink slime, you should chemical clean the filter as well. ...