A blue gel ant farm contains all the nutrients and moisture in the gel your harvester ants will need. You don't have to feed or water the harvester ants, but you need to clean their habitat from debris and dead harvester ants. In nature, worker ants are responsible for keeping the habitat clean, but in a closed system, you need to do it for the harvester ants. Depending on the manufacturer, the gel lasts for a year or the life cycle of the harvester ants. Replacement gel isn't available, which means you need to purchase a new unit. Sand-filled aquariums require more work than gel aquariums but are a more natural habitat for the ants. You need to feed and water your harvester ants regularly; the sand doesn't contain sufficient nutrients for them.