Which liquids are safe in a liquid feeder, and how often should I change them?
Plain water or sugar water. Those are the only two things we put in a liquid feeder.
Most colonies do best with two feeders in the foraging area, one of fresh water and one of sugar water, so they always have both. For the water, use distilled, purified or spring water. Check them once a week and top them up. Our Liquid Feeder comes in two sizes, 2.3 ml for founding and small colonies and 4 ml for bigger ones, and its glass vial unscrews for refilling and washing.
Skip honey-water. It ferments quickly in a feeder. If you want to give your ants honey, dilute a little and offer a drop on a feeding dish instead. That's how we use our Honeydew Honey.
Protein doesn't go in a liquid feeder either. Offer pre-killed insects in a dish and clear the leftovers within a day.