Charcoal filter?

Intro: I've been lurking for a few weeks and decided it's time to take the
plunge. My son was given permission to catch goldfish (net) at pond and came
home with 6 very nice comets, ranging from 4 to 9" length. They have been
living in a 37 Gal tank (too small!) while we build a pond for them. We
purchased a 150 gal preform and have put it in the ground. I bought a 1400
gph pump at a fish auction and am starting to build the filter. I have
decided on a 55 gal barrel filter with an up flow gravel bed and plan on
having WH floating in the top as a veggie filter. I know that charcoal
briquettes are only sawdust and glue and some sodium nitrate to speed up
burning, and given this composition, are totally unsuitable for aquatic use,
however, my local food Coop sells natural chunk hardwood charcoal with no
additives. Would this be effective as a filter material, at least while
cycling, and in the future to clear meds, etc?

Jeff Lowe