Barry,
I had them in my chalice tank. I used FW Exit and followed the instructions. Mine came back just like Charlie said. I think it kills the adults but not the babies. They might be hiding in the recesses of the LR so are not exposed as much the adults, perhaps? If yo do use it, siphon as many out as you can before you treat, and get as many after you treat.
I treated like 4x with FW exit, and finally gave up 'cause it was looking like a waste of money.
Mine eventually went away on their own. I think they are a response to an increased food source within the tank, either too much feeding, something dying they are feeding on, or a combination of the above.
You might look at reducing your feeding, and increasing water changes and prefilter maintenance. Then see if their population settles out. Mine just went away after a while.
