i cured 11 of my clams with this treatment(lost 7 beforei did this)
if you can remove the clam to a QT with great lighting, do it.
then get a reactor,canister filter or even a 2"pvc pipe, anything large enough to put at least 1L of carbon per 100gal(the more carbon the better)the water has to be pumped through the carbon at least once per hour total system gal, a bag full of carbon thrown in the sump or tank isnt going to work.
then give the clam a 20 min FWD to kill off as many protozoan as you can to start.