Aquarium lighting options for a healthy fish tank

The correct aquarium lighting depends on the individual set-up and the light requirements of the tanks inhabitants.

Lighting influences the growth of your aquarium plants, corals, and invertebrates as well as the behavior of your fish. Incorrect lighting will result in many problems, as it is directly related to photosynthesis, CO2, and nutrients.

Appropriate aquarium lighting that meets the requirements of your set-up will enhance the overall appearance and health of your fish tank.

The most common aquarium light sources:

Incandescent
Halogen
Fluorescent
High Intensity Discharge
LED

Before we get started, lets put some definitions in plain English. They are essential for an understanding of the different applications.

The light spectrum describes the combination of colors of which the light consists of. Namely red, yellow, green and blue (rainbow colors).

These spectrums are measured as “color temperature” – Kelvin (K).

Red and yellow produce lower temperatures while blue light produces a higher temperature. Lower and higher defined as the basic sunlight with 5500 K.

The Color Rendering Index (CRI) is indexed on a scale from 0 – 100.

100 being the equivalent to sunlight and how objects would naturally appear. CRI is an expression of the degree to which the illuminated objects appear according to their true natural color.

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The intensity of light is given as Lux or lumen. This is very essential, because a light source moved only 2 inches away from the water will be 4 times less intensive. So even if the light source is correct, it might still be insufficient, depending on the distance to the area to be illuminated.

Some General Facts about Aquarium Lighting:

Too much red light could stimulate algae growth in the aquarium. In this case we are talking about 4000 K.

Always select the light in the aquarium according to the natural habitat of your fish. Too much light will not blind or fry them, but they may cause your fish to find places to hide.   Dust, humidity, water turbidity and dirty vinyl or glass covers will influence the light as well. Intense lighting can lead to increased algae growth. Combined with silicates the result will be brownish algae. Combined with phosphates the result is more red and greenish algae.  You should adjust your aquarium lighting to meet the needs of your set-up and inhabitants. There are always possibilities and creative ways to shade some areas with overhangs.

Incandescent Light (basic light bulb) and the Improvement of the Halogen Light

A CRI of 100 has a heavy red spectrum. The color temperature is 2700 K for incandescent light and 3000 K for halogen light.  This type of lighting should only be used as a supplement for good plant growth due to the increased development of heat.

Fluorescent Light

All fluorescent tubes should be replaced after 6-12 months. Their loss of output over time is significant. This is not visible to the eye however. Different types are available. Life forms requiring low light will do fine with regular tubes. Corals, polyps, and light intense life forms will prefer HO (high output) or VHO (very high output) tubes.  Full spectrum tubes, come as close to the sunlight as possible. There a combination might be advisable, as corals need a more blue color spectrum. Of course there are special tubes for plant growth, which work with blue and red spikes (red is especially needed for plant growth) which promote photosynthesis.

Remember that the red color also enhances algae growth.

Halide Lighting

Halide bulbs are more costly but will provide very intense lighting. Best suited for plants and invertebrates. As a rule of thumb, 3-5 Watt per Gallon of lighting will be the range, but always consider, that light is energy and it really depends on the animals and plants living in the tank.

Also see our post about ‘Lighting the aquarium with LEDs‘ here!