Ivermectin in the main tank is a big no-no. I have accidentally introduced it and it killed pretty much all inverts with the exception of acoels. I use it as a bath for 1-2 hours, followed by a rinse in sea water, followed by 24 hours in a holding tank running a large amount of activated carbon. I would only use it in the main tank as a last resort after removing all inverts (especially snails, crabs, shrimp, etc.). It has an approximately 8 month half life in water vs ~8 hours for interceptor. Dangerous stuff but very effective. All waste water containing it needs to be cloroxed for 24 hours or more, as it is very toxic in local waterways.Have you not tried Interceptor yet? I just read again your entire thread and don't see that you tried that. I'm glad I did read it again because I apologize for missing that the parasite is a mite, not a tegastes copepod like what I was dealing with. (I was basing all my earlier recommendations on my experiences with tegastes "bugs," not mites). With either parasite, it would probably make sense to try Interceptor before trying any of the other drugs (KCl, malathion or ivermectin) since we know a dosage that works at least for Red Bugs. (Interceptor can also be used for skin mites on dogs so we know it is good for at least some mites). But now that I realize it is a mite, if it was me, and Interceptor didn't work, I would go right to Ivomec as @sculpin01 has been suggesting. I've used Ivomec for years to kill microscopic burrowing mites (knemidocoptes) in parakeets and they are easily eliminated with just 1/5 of a drop placed on the skin. Of course it is a different mite, but Ivomec is certainly a drug of choice for mites. Sorry I didn't catch this earlier.
FWIW, the dosage of Ivomec in the article that Sculpin01 mentioned was about 10X more concentrated than the dosage that I used for telegastes which didn't kill them. However, my weaker dosage was plenty to paralyze worms, including Bearded Fire Worms which makes me think the article's dosage of 2 ml/2.6 gal is a whopping dose and perhaps should only be used as a dip or bath and could be potentially dangerous to use in a main tank. ??