If you have a sump, you can put some in a bag in the sump. Or put some in your media reactor with Rowaphos. Just throwing out ideas. Amphidinium is not supposed to be very toxic, but mine was. Using GAC kept my animals alive until dinos subsided. FWIW I think you are on your way with removing sand and si dosing.I only have one media reactor ...and I run rowaphos in that