What is cheapest online source of ascorbic acid?

[vanduse1]

The steps for Ascorbic Acid indicate that you need to turn your pump on circulate instead of filter. I don't have the option to bypass my filter. I do have a second pump that powers the water features but don't know if that will circulate the pump well enough. Is it a big deal to not use the filter at first when adding ascorbic acid?

[mbar]

You can just leave the pump on filter - it will still work. Good luck