Hi Dianne,
Camallanus are livebearers and they can only live in water, so there is no
way for the fishes to be infested by nonwater-animals!
The problem with camallanus is, that the time from the larva-state to the
adult state, when the breeding females are visible at the anus of the
fish, is three month!!!
So if it was about three month ago, when you had the infestation, it is
possible that not all worms and larvas were killed.
I don't know Ivermectin on myself, but there were a lot of messages in the
list before, saying that it works fine.
Another medicine, that I have used, is "Concurat L 10%". That has worked
very good, the worms were gone without any loss of fishes and the fishes are
absolutely ok. And they breed normal.
So maybe you have used Ivermectin not long enough? I don't know.
Regards, Karsten