Aquarium Light VS Grow Light – Know Which One To Choose

In this article, we take a closer look at aquarium light vs grow light. If you’re into hydroponics and indoor gardening, you’ll want to know if you can use regular LED aquarium lighting to grow your plants, or do you need a special horticultural grow light? Also, is it more cost-effective to use an aquarium plant light for your fish tank set up if you have live plants and fish, rather than a regular tank light?

Read this guide to find out!

Aquarium Lights vs Grow Lights – Comparison Table

Here’s a quick summary of what kind of lighting can be used for aquarium lights vs grow lights, as well as the measurement applicable to both.

Aquarium Lights vs Grow Lights

What’s the difference between a grow light and an aquarium light?

The difference between a plant grow light for growing terrestrial plants, and an aquarium light is generally the unit’s spectral output. Aquarium lights usually have more green and less red and blue, which gives the light they produce a more appealing look, although it’s not ideal for plants, which need more red and blue light for healthy growth.

Kelvin rating

The primary difference between aquarium and grow lights is in the Kelvin rating. So, what is the Kelvin rating?

In science, Kelvin is defined as:

“… the SI base unit of thermodynamic temperature, equal in magnitude to the degree Celsius.”

In plain English, Kelvin is used in lighting to measure the color temperature of a light bulb. Basically, the higher the Kelvin rating (k) of a light bulb, the whiter the light produced by that bulb will be.

Grow lights and lights specifically designed for use in tanks containing aquatic plants are generally given a Kelvin rating of between 4,700k to around 6,700k and emit a pinkish-white light, which is the optimum range for photosynthesis and pretty much equates to natural daylight.

Aquarium lights for reef and marine tanks are generally more toward the 8,000k range and above, producing a bright white through to blue spectrum.

Terrestrial Plants

The spectral output defines lights that are designed for growing terrestrial plants. Plant lights generally have a lot of reds and blues, which are most effective for the process of photosynthesis.

Aquarium Lights

So, to summarize, aquarium lights produce a bright white through to blue light that’s designed to show off your fishes’ colors, as well as provide adequate lighting for easy to care for aquatic plants. More challenging plant species need more red and blue light to thrive.

Planted Tanks

Many aquatic plants that are popular with hobbyists are very easy to keep and grow. However, you’ll need to ensure that the plants receive adequate light if they’re to remain healthy and thrive.

Generally, carpet plants, those that are low-growing, and those with red or purple coloration require higher light levels than other species, which can present a challenge, especially if you have a deep tank that houses light-sensitive fish or other creatures.

Paludariums

If you keep a paludarium, you’ll need to choose lighting that suits both the creatures that live beneath the water and the plants that dwell above it. One way to avoid conflict is to use plastic or silk planting, which can look equally effective without giving you the headache of finding lighting that suits both environments.

You might be interested on our article about Riparium vs Paludarium. Read about it here.

Lumens and Watts

Lights are also measured in lumens and watts. So, what’s the difference between lumens and watts?

Lumens

Lumens are the measurement of visible light that’s given off by a light source, which you can measure with a light meter.

Watts

Watts is the measurement of the electricity that a device uses, for example, an aquarium or grow light fitting. Watts refers to how much energy a device uses or its energy consumption and is not related to the amount of light a bulb produces.

Watts vs Lumens in Aquarium Lights

When choosing aquarium lights, the lumen value is always shown on the packaging. Previously, light bulbs or tubes were classified in watts to reflect how much electricity the bulb used. That makes it tricky to compare the amount of light a unit will produce because bulbs, LEDs, and fluorescent tubes are not directly comparable in that respect.

The lumen value that you need for your tank really depends on whether you have live plants or not. Fish don’t need light to be happy; we only illuminate our aquariums so that we can admire the contents.

Plants, however, need light for photosynthesis, and without light, your plants will die. The amount of light you need depends on the kind of plants you grow. You can read a detailed article about choosing lighting for aquarium plants in the article at this link.

As a basic guideline, 20 lumens correspond to 0.5-watt T5 tube per liter or 40 lumens to 1-watt T5 tube per liter.

What are the Types of Aquarium Lights?

There are several kinds of aquarium lights:

Normal Output Fluorescent Lighting

Normal output fluorescent lights are very versatile lighting systems and are the simplest and most popular way of illuminating your fish tank. There’s a huge range of bulbs to choose from to suit your requirements; they’re cost-effective and energy-efficient, enabling you to customize your lighting set up exactly as you want it.

Compact Fluorescents

Compact fluorescent lights are a higher-output version of normal output fluorescent light systems. Rather than a single tube, compact units feature dual or quad tube bulbs to create much more illumination than you would get from one bulb, essentially giving you more bang for your buck.

Metal Halides

Advanced hobbyists use metal halide lighting systems. Metal halide systems comprise a primary glass bulb connected to another bulb (arc tube) within it. These lights are often used for reef tanks where the inhabitants require high light levels or very large, deep tanks. Metal halides tend to emit high levels of heat and are more expensive to run than other options.

LED (Light Emitting Diode)

LEDs are becoming extremely popular in the hobby, as they use far less energy to produce very bright lighting, offering a viable alternative to metal halides for reef tank lighting. They also have a much cooler operating temperature than other lighting options, keeping your water temperature more stable than other lighting systems.

Can Aquarium Lights be Used as Grow Lights?

Although, in theory, you could use certain aquarium lights for growing terrestrial plants, you may get better results by using a brighter, higher spectrum horticultural lighting unit.

Grow Lights

Grow lights are used to provide a similar light spectrum to that of the sun, specifically to boost terrestrial plants’ healthy growth. Grow lights can be tailored to provide specific spectral ranges, color temperature, and luminous efficacy to suit the species of plant and stage of cultivation.

Spectral Output

As mentioned previously, when choosing grow lights, it’s the spectral output that’s most important.

Plants primarily absorb blue and red light to grow and flower. Blue light stimulates plant growth, while red light encourages growth and flowering.

A correctly balanced spectral output is vital, as too much blue light and not enough red light will produce stunted growth with thick stems, few flowers, and dark green leaves. Too much red light provides plants with elongated stems and tall, spindly growth.

Types of Grow Lights

There are several kinds of grow lights that are suitable for terrestrial horticulture.

T5 High Output (HO) fluorescent tubes

T5 HO fluorescent tubes are the most popular choice of grow lights and can also be used for aquarium lighting.

HO fluorescent tubes produce strong light that encourages good growth and flowering, are long-lasting (approximately 22,000 hours), are inexpensive, economical to run, and give off little heat.

LED (Light Emitting Diode)

LEDs can be used as grow lights and are long-lasting, cool-operating, and more energy-efficient than T5 HO fluorescents. However, they are more expensive to buy.

High-Intensity Discharge (HID) Lights

HID lights include metal halide and high-pressure sodium systems. Although advanced horticulturalists sometimes use these systems, they give off a lot of heat and require extraction equipment to remove the hot air.

Can grow lights be used as aquarium lights?

So, you can see that some forms of grow lights can double as aquarium lights if you have a planted tank.

In Conclusion

I hope you enjoyed our comparison between aquarium light and grow lights. As you can see, there is some crossover between the two, although there are some key differences too.

If you keep an aquarium that doesn’t have living plants, the intensity and color of the lighting you choose will depend on the preferences of your fish and other tank residents. However, if you have live plants in the tank, you will need to choose lighting to suit their needs. To further complicate matters, if you keep a paludarium, you’ll need lighting to suit your livestock and terrestrial plants.

We’d love to know how you manage the challenge of lighting your tank! Share with us in the comments box below.