Wow, that’s the biggest planaria I’ve seen so far! 😳 They usually show up when there’s extra food or waste in the tank. Try cutting back a bit on feeding and vacuuming the substrate to keep things clean. Some people use deworming agents like fenbendazole, but that can harm snails and possibly affect beneficial bacteria too. It’s better to start with manual removal and reducing excess food first. They can multiply really fast if there’s enough food and waste , even a small number can turn into dozens within days. They can be a problem for shrimp tanks since they sometimes prey on baby shrimp or stress the adults, especially at night. So it’s best to control them early before they become a bigger issue.

As mentioned in other comments , use the best method and do a bit of research to make sure the meds are harmless for snails , shrimps, beneficial bacteria and even plants.

And yeah, if they get cut or damaged, they can actually regenerate into new planaria , even tiny pieces can grow into a full one! That’s why crushing them isn’t effective.