I keep it in there all the time, changing the garlic weekly and the cider daily. I put one clove for every gallon. I put four or five cap fulls for each gallon of apple cider.
Welcome! Personally i like to use natural remedies, because with the other chemicals you cant eat the eggs for about two weeks. Cucumber or squash is good, the raw seeds paralyze the worms. Also, put apple cider vinegar in their water, as well as crushed garlic. I hope this helps!