Along with water, hydroponics plant nutrients, CO2 and oxygen, grow light is the key basic component, required by plants to live. Providing additional light is necessary for indoor gardening. Furthermore, light should resemble the sunlight as much as possible. The major concern with other types of lights is that they do not produce light in the appropriate spectrum, required by plants.

Being the most efficient bulbs, HPS bulbs are commonly used by gardeners. Producing light in red and yellow spectrum, light generated by high pressure sodium lamps resembles the natural sunlight during autumn. Due to this peculiarity, HPS light is the best for promoting plants blooming. However, some plants may react negatively to this type of light, growing with oblong stem, etc. To address that issue, new HPS bulbs with color correction have been developed. For example, Son Argo feature properly balanced light spectrum, which suits perfectly for the needs of indoor gardening.

High pressure sodium grow lamps are made of a semi-transparent ceramic arc tube, filled with a mixture of sodium, mercury, and xenon. The arc tube is placed into the protective outer glass shield, similarly to metal halide bulbs. The power ranges of HPS bulbs vary from 35w to 1000w, while the most popular are 250w, 400w, 600w and 1000w.

HPS bulbs are more durable in comparison with MH bulbs: they can be replaced once every 24 months. Though HPS grow lights lose their brightness slowly, in order to keep the brightness at the steady level, it is still recommended to replace the bulb within the specified period.

Among the brand new types of grow lights are sulfur lights, which are said to feature extremely high brightness and effectiveness. However, these bulbs are still rare on the market in view of the high price, so it is early to evaluate their practical value for those gardeners, for whom indoor hydroponics growing remains a hobby.