To provide a luminaire for a water tank, which adjusts emission intensity and colors of emitted light, while having power saving effect, high usage efficiency, a long lifetime, and a low cost.

The luminaire for the water tank includes an illumination unit 21 and a control unit 22. The illumination unit 21 has a plurality of light emitting diodes 211. The light emitting diodes emitting light in different colors are installed adjacent to each other, and the control unit is electrically connected to the light emitting diodes 211 to adjust the light emitting diodes emitting light in different colors.