Minerals in well water or softened water may be detrimental to plants. Some gesneriads like Chirita and Gesneria require continuous amounts of water. Others, like Achimenes, become dormant if allowed to dry out even once. Some gesneriads will tolerate or do quite well in a moderately sunny window as long as the temperature isn't too high and water requirements are met. If necessary, shade the plants with a curtain, or move them away from the window.
Most gesneriads grow and bloom very well under artificial lights.
Fluorescent light setups are available at many department stores and nurseries or you can construct your own. Cool white lamps are adequate, but more expensive daylight types exist that better simulate natural light. Lights should be turned on for 12-16 hours per day. Lights should be hung an average of 8-16 inches above the plants. Most gesneriads come from humid tropical areas.