Fenbendazole, aka panacur. It will kill off some other inverts. For instance, worms do not tolerate it. Some snails are okay with it, some aren't. My point being take out any valuable inverts, and watch your ammonia levels in case you have significant die off.
I get the paste from farm supply stores, and use about 1/4 inch strip (it comes out like tooth paste). Put it in water, shake REALLY WELL to emulsify, and add to tank. Do a 1/3 water change 24 hours later.
I don't recall the dosage for the granules, but I'm sure you can google it.