10K Vs. 20K Saltwater Reef Lights

Proper lighting in a saltwater coral reef tank is probably the most important aspect for a well-balanced and thriving environment. Corals have specific needs in color temperature, or Kelvin (K) rating, to sustain life. Both 10K and 20K lights have advantages and disadvantages.

  1. K Ratings

    • Midday sunlight on the surface of saltwater over a shallow coral reef has a K rating of 6500 or 6.5K. On the color spectrum, it is slightly on the blue side. A higher K rating equals a bluer wavelength, and a lower K rating equals a yellower wavelength.

    10K Bulbs

    • Bulbs that are 10K are bluer than the optimal 6500 temperature and provide adequate energy, but coral growth with 10K bulbs is somewhat slower. The 10K bulbs also are not as yellow, however, and appear brighter, making the tank more visually appealing.

    20K Bulbs

    • Bulbs that are 20K are darker blue and beneficial to deeper saltwater soft coral, mimicking the sunlight at greater depths. Their darker blue color also serves to bring out the fluorescent pigments of the coral, creating what can be considered a breathtaking visual experience. Shallow saltwater corals do not benefit from 20K bulbs, however, and have little or no growth with them.

    Recommendation

    • Using a mixture of lights is recommended. They should be visually satisfying while maintaining a balanced system.