Aquarium Light VS Grow Light

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 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 setup if you have live plants and fish, rather than a regular fish tank light?

Read this guide to find out!

Aquarium Lights vs Grow Lights – Comparison Chart

Here is a quick summary of what type of lighting can be used for aquarium lights vs. grow lights, as well as the measure applicable to both.

Characteristic aquarium lights grow lights
Kelvins Yes, if it is for planted tanks. Yes
Spectrum Planted tanks only Yes
Watts Yes Yes
lumens Yes Yes
LED lighting Yes Yes
Normal output fluorescent lighting Yes Nope
compact fluorescent Yes Nope
metal halides Yes
High Output T5 Fluorescent Tubes (HO) Yes Yes
High Intensity Discharge (HID) lights Nope Yes

Aquarium lights vs grow lights

What is 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 spectral output of the unit. Aquarium lights typically have more green and less red and blue, which gives the light they produce a more attractive appearance, though not ideal for plants, which need more red and blue light for healthy growth.

Kelvin Rating

The main 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 (k) rating of a light bulb, the whiter the light produced by that bulb.

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

Aquarium lights for reef and marine tanks generally go closer to the 8,000k range and higher, producing a bright white to blue spectrum.

land plants

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

aquarium lights

So to summarize, aquarium lights produce a bright white to blue light that is designed to show off the colors of your fish as well as provide adequate lighting for easy care of 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 maintain and grow. However, you will need to make sure the plants are getting adequate light if they are to stay healthy and thrive.

In general, carpet plants, short growers, and those with red or purple coloring require higher light levels than other species, which can be challenging, especially if you have a deep tank that houses fish or other sensitive creatures to the light.


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

lumens and watts

The lights are also measured in lumens and watts. So what is the difference between lumens and watts?


Lumens are the measure of visible light. emitted by a light source, which can be measured with a photometer.


Watts is the measure of electricity used by a device, for example an aquarium or grow light. Watts refers to the amount of power a device uses or its power 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 light tubes were rated in watts to reflect the amount of electricity the bulb used. That makes it tricky to compare how much light a unit will produce because light bulbs, LEDs, and fluorescent tubes aren’t directly comparable in that regard.

The lumen value 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 light 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 type of plants you are growing. You can read a detailed article on the choice of lighting for aquarium plants in the article at this link.

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

What are the types of aquarium lights?

There are several types of aquarium lights:

Normal output fluorescent lighting

Normal output fluorescent lights are very versatile lighting systems and are the simplest and most popular way to light your fish tank. There is a wide range of bulbs to choose from to suit your needs; they are cost effective and energy efficient, allowing you to customize your lighting setup exactly how you want it.

compact fluorescent

Compact fluorescent lights are a higher output version of normal output fluorescent lighting systems. Instead of a single tube, the compact units feature dual or quad tube bulbs to create much more lighting than you’d get with 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 operate than other options.

LED (light emitting diode)

LEDs are becoming extremely popular in the hobby as they use much less power 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, which keeps the 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 to grow terrestrial plants, you may get better results if you use a brighter, broader spectrum horticultural lighting unit.

grow lights

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

Spectral output

As mentioned above, when choosing grow lights, it is the spectral output that is most important.

Plants mainly absorb blue and red light to grow and flourish. Blue light stimulates plant growth, while red light stimulates growth and flowering.

Properly balanced spectral output is vital as too much blue light and too little red light will result in stunted growth with thick stems, few flowers and dark green leaves. Too much red light gives plants elongated stems and tall, spindly growth.

Types of grow lights

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

High Output T5 Fluorescent Tubes (HO)

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

HO fluorescent tubes produce a strong light that promotes good growth and flowering, are long-lasting (approximately 22,000 hours), are inexpensive, inexpensive to operate, and emit little heat.

LED (light emitting diode)

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

High Intensity Discharge (HID) lights

HID lights include high pressure sodium and metal halide systems. Although advanced gardeners sometimes use these systems, they give off a lot of heat and require exhaust 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 have enjoyed our comparison between aquarium light and grow lights. As you can see, there is some crossover between the two, although there are also some key differences.

If you keep an aquarium that does not have live plants, the intensity and color of 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 that suits your needs. To further complicate matters, if you have a paludarium, you’ll need lighting that suits your livestock and terrestrial plants.

We’d love to hear how you handle the challenge of starting your tank! Share with us in the comment box below.

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