Originally Posted by kribbz
saifert also manufacures a product called flatworm exit that works pretty well just be sure to dose a little more than the instructions say.
Flatworm exit does indeed work but sometimes at a cost. This will kill every flatworm in the tank when dosed slightly more than recommended.
It is very
important to remove as many as possible before administering the treatment. When the flatworm dies, it releases a very potent toxin into the water which if the concentration becomes too high will damage animals in the tank, fish are the primary ones hit. Syphoning the pests out can be a pain, but it will minimize much of the risk.
It is also advisable to have several changes of carbon at hand as well as 25% change water at the ready.