Order some Joe's Juice or use use a kalk
solution in a syringe or boiling water or lemon juice in a syringe.
If you are already infested they will keep coming back. The only way to rid the tank of them at that point is to "cook the rock"...That does not mean putting it in a 350 oven. It means putting it in a container with fresh sw
mix a heater and ph, but covered so it gets no night. Every two weeks move the rock to another container of fresh sw
(need at least two buckets/containers. It could take a full year of cooking to kill all the manjo.