I treated my qt tank for camallanus worms before using 100 mg/10 gallons of levamisole. The worms turned clear for a while before turning dark red again. I then upped the dosage a bit later to 500 mg/10 gallons, same thing, nothing is being passed, just clear then they get red again. Is this resistance and if so what do I do now? I can move my snails out into a bucket during treatment if I need to do fenbendazole but I can't find any medicated food.