I keep small colonies of Temnothorax curvispinosis and Temnothorax longispinosis that have roughly 25 -50 workers each. I've mostly found them living in acorns, once in a walnut.
I use small pieces of sponge to feed them sugar/water and water. I place the sponges on a small plastic feeder made from the security lid of a cream container.
Many of the small ant species that I keep are timid and don't seem to like feeding in the open. I find they accept food (protein) more readily if it's covered by something, so I place insect pieces under the plastic feeder, close to their acorn. They send out one or two foragers and never take a lot of protein at any one time. Mine seem to like insects like mealworms, crickets, earwigs, fruit flies and flies - cut up in small pieces. They raise small amounts of brood so only require small amounts of protein compared to most of my other ants.
My father always said I had ants in my pants.