A high humidity gypsum based formicarium, compact in the form of a test tube. These formicaria are great in that they provide a comfortable and natural-feeling habitat for your ants. They are watered using a sand reservoir which lasts up to a week.
In terms of the ants' well-being, these are some of the best formicaria on the market. However, keep in mind that visibility may be limited due to condensation and that they are unsuitable for more destructive species.