Soooo, just tok the plunge & dosed tank with recommended amount of flatworm exit. Siphoned off all I could get to prior to dosing. About 5-10 min later it was apparent that I didn't siphon off nearly as many as I thought, skimming wet & running large amount of carbon. So far can't see any adverse effects from the toxins released by dead worms, lots of dead ones in the water column. Will do 25% water change in the next half hour. So far so good but keeping fingers crossed. Will update later.