The Best Lighting for 20 Gallon Long Reef Tanks

After filtration, lighting is one of the most important elements to consider when setting up a reef aquarium, which is an aquarium that contains corals. A 20-gallon long reef aquarium would be considered a nano reef tank, which can be difficult to maintain. Finding the best lighting isn't difficult -- you just need to make a few considerations.

  1. Size

    • The first consideration to make is size. A 20-gallon long aquarium is 30 inches long by 12 inches wide, therefore you need a light fixture that's at least 30 inches long so that it covers the entire top of the aquarium. Because you will need multiple bulbs, you will will need a fixture capable of holding up to four fluorescent light bulbs.

    Wattage

    • The wattage of the lighting is one of the more important aspects and affects the light's intensity. As a rule of thumb, corals need approximately 3 to 5 watts of light per gallon, with softer corals desiring less wattage and harder corals desiring more wattage. If using the average of 4 watts per gallon, a 20-gallon tank would need about 80 total watts of lighting, which can be accomplished using multiple fluorescent light bulbs. Because of this, you will need to get a light fixture that is capable of holding multiple bulbs. Most bulbs come in 24-watt varieties, so you will need four.

    Temperature

    • The temperature refers to the intensity of light in Kelvin. Different corals have different requirements and different levels of sensitivity; therefore, it is important to know what type of corals you will be keeping in your reef tank before purchasing and do independent research. However, most corals fall within the tolerable range of 5,000 to 10,000 Kelvin, which is adequate to simulate natural daylight.

    Color

    • Different colors are designed to simulate filtered light at various water depths, and though your tank is only 12 inches high (equating to 12 inches of water depth), most of the corals you will place in it will probably be used to light with a 420nm wave length. You can simulate this wave length using white blue actinic light, which is a mix of white and blue light and also makes colors on corals pop. When selecting a color for your bulbs, you can either alternate white and blue actinic lights (2 white, 2 blue) or use 50/50 white-blue bulbs, which mix the colors.

    Timing

    • The goal of the lighting in the reef tank is to simulate natural conditions, with one of these conditions being the rising and setting of the sun. As such, it is recommended that you use a dimming switch on your light fixture and run the lights at half power in the mornings for an hour before turning it to full power to simulate a rising sun. Conversely, set the lights to half power an hour before you turn them off completely at night to simulate a setting sun. Many dimming switches come with timers to make this easier to manage.