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The 5 Best UV Grow Lights

UV grow lights can greatly improve your growth quality if used appropriately. Too many “full spectrum” lights are not truly full spectrum. Many do not even consider UVB lights. Don’t be tricked by marketing hype. Read below to learn more about UV grow lights

Our top recommendation is…

Greenpinky’s top pick:
  • UVB wavelengths
  • Quality build
  • Great price
Check Amazon for Best Price

When used incorrectly, UV light can bleach the color right out of your crop. However, when it is used properly it can increase pigmentation, which will give your crops a beautiful color. It can even be used to increase flavor and aromas

Let’s take a look at the best UV lights and how to use them properly.

Comparing Our 3 Top Recommendations for UV Grow Lights

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Best UV Grow LIghts

The Best UV Grow Lights

These are our top recommended UV grow lights for plants.  UV lights are a hidden gem within in the hydroponic world. Below are some short reviews and descriptions of our best picks.

UVA Grow lights

Best UV Grow Lights

California Light Works’ UVB Grow Light uses UVB lights to help induce a stress response in your hydroponic growths. By stressing your plant, it will produce shinier, richer-colored leaves as well as produce resins that will amplify the taste and smells released by your plant. If you are looking for high quality growths, UVB lights will help you reach that goal.

Please read more below as to how to use them properly. Using them incorrectly can lead to more damage than good. Light Work’s system is meant to be hung about 3 feet above your plant’s canopy and it covers a 4×4 area. It utilizes a UVB 25 watt T5 fluorescent light.

If you are looking for a replacement bulb, you can buy a California Light Work’s bulb or you can consider our top recommendation for a UVB bulb below, which is significantly cheaper and works just as well.

Agromax’s UV Grow Light is the best replacement UVB grow light. It is not only priced at an exceptional price point, it also works well. If you have a grow light, such as the California Light Work system mentioned above and need a replacement bulb, this is the one to get. It will also work with any other T5HO fixture (T represents the tubular shape and 5 represents the tubes diameter in eights of an inch; T5 = Tubular 5/8” diameter. HO represents high output). Similar to what I said above, make sure you read further below as to how to appropriately use UVB lights with your plants.

Please note, as is clearly stated in the product description. This is merely a replacement bulb. Do not mistakenly buy this thinking that it is a completed UVB grow light system. If you are looking for a complete UVB grow light, please see the California Light Work system above.

This grow light is one of the few LED grow lights that are truly full spectrum. This 3000W CREE COB LED light is known for its high power and stability. It has a longer life than normal LED lights as well as higher brightness. It contains 6 COB lights, 100 630-660nm lights, 12 470nm lights, 12 6500K lights, 6 IR lights, and 4 UVA lights.

Phlizon recommends hanging this light at a height of 24” and has a coverage area of 4×4’. They include a 30 day money back guarantee. If you can afford it, this a great light that does not put out high temperatures like the usual high pressure sodium lamps and also is truly full spectrum.

Mars Hydro has created another fantastic grow light with their SP 250 Full Spectrum Grow Light. It comes only 230 watts and puts out a whopping 925umol at 18”. It is designed to replace a 2000 watt HPS. The lights themselves are truly full spectrum covering the gamut of UVA to blue lights and red lights. It is also set up to be IP65 waterproof, so you do not need to worry about the humidity of your grow room or grow tent damaging your light. It utilizes a fan-less design for heat dissipation, which means no whirring noise of a fan.

For the price, this is truly a well-designed, quality light that contains UVA light wavelengths.

Aqua Advantage Inline sterilizer is mean to be installed in-line with your system to help destroy pathogens as well as algae. Many people use it in their aquarium builds to purify the water, but it works just as well in a hydroponic system to keep the water clean. This 8-watt sterilizer uses UVC rays to help purify your water. It does so in a purely physical manner so that no chemicals need to be added that may damage your hydroponic plants or that may alter your nutrient ratios.

The inlets and outlets utilize 3/4″ barbed fittings. The manufacturer recommends a max flow rate of 1000GPH. Note that this is meant to be put in-line and is not meant to be submersed in your hydroponic tank. It is recommended that you keep it running 24/7 to control the germs and pathogens in your hydroponic system. The light itself does not transfer any significant heat to the system.

UVB Grow lights

Ultraviolet Grow Light Guide

Ultraviolet lights can be very effective when used properly. When used incorrectly they will damage or potentially even kill your plants. Let’s take a quick look at the different types of UV lights and how they should be used to help improve your growths.

Different Types of UV lights

It depends on which specific wavelength of UV’s are used and how they are applied to your plants.

There are three different categories to UV lights. UVA, UVB, UVC.

UVC Light is for Sterilization

UVC is 100-280nm. UVC is the shortest wavelength of the UV lights. It is extremely destructive. This is why UVC is used as a germicide to destroy microorganisms.

In nature, most UVC is absorbed by the ozone layer.

UVC can be used in a hydroponic setting by being applied inline to help sanitize the nutrient solution that will be feeding the plant. It can also be shined directly on top of the plants to kill pathogens (it can kill pathogens like powdery mildew).

UVC lights need to be used very careful. It can be destructive. When you are using it in-line, only the water would be exposed to the light so there will be no risk of damage to your plants (or to yourself). When it is used overhead to destroy pathogens, usually it is only on when you are not in the garden itself – this will minimize damage to yourself.

UVC lights can also help prevent or rid your system of algae when set in-line with your hydroponic system. Our recommendation above is for an inline system because of how effective it.

UV grow lights for hydroponics

UVB Light is for Inducing Stress and Producing Flavor

UVB is 280-320nm. Most of the UVB is also absorbed by ozone layer.

UVB usually is the UV rays that cause sunburns. When applied to plants, it can cause a stress response in plants. This can result in the increase production of pigment, antioxidants, and resins. These are defensive responses that help to boost flavor. Visually, your plants’ leaves will be shinier and more vibrant.

How to Use UVB Lights

When you turn on your UVB light, it may not look like it is putting out a lot of light, but trust me, it is strong and enough for the plants you are growing. Plants are very sensitive to UV lights, so they do not need much.

UVB should be used at the end of a growth, preferably in the last week. UVB can actually slow down growth (because of the stress it puts on the plant). So you want to wait until your plants growth has peaked and use it in that final weak to help ripen the growth that is already present.

When you are using your UVB light, test it in small doses – hours at a time. This is because different plants are affected by UVB differently. You can get drastic results with small doses.

Set the UVB light about 3 feet above the plant canopy. If you need replacement bulbs for the California Lightworks UVB light, you can either buy it directly from them, or spring for the Agromax 24” replacement bulb

UVA Lights Bring Out the Darker Pigments

UVA is 320-400nm, the longest wavelengths within the UV spectrum.

UVA causes the inhibition of cell elongation. This will help create shorter plants. It can also be used to further simulate the growth of red and purple pigments in your plants’ leaves.

UVA can readily be found in many full spectrum lights including T5 fluorescents, metal halides, ceramic metal halides, and certain full spectrum LED lights. These usually have enough UVA to provide the benefit of shorter growths with more red and purple pigmentation.

Be Careful, Protect Your Eyes!

Please be aware that being around UV lights for too long can be dangerous (particularly UVC and UVB lights). Try to turn off the light before entering the grow room. If you must leave it on, try to stay far away from the lights to minimize the potential damage to your skin and also make sure to wear protective glasses.

Bottom Line

The best UV grow light will depend on what your goals are. Our recommendations for the best UVA grow light is Phlizon CREE COB 3000 Full Spectrum LED Grow Light, UVB grow light is California Light Works’ UVB Grow Light System, and UVC grow light is Aqua Advantage UV Sterilizer Inline. The most frequent UV found in full spectrum grow lights is UVA. That being said, many full spectrum grow lights don’t even contain UVA. No full spectrum grow lights contain UVB or UVC. But used appropriately, particularly UVB grow lights, it can really boost the quality of your harvests.

About the author: Carley Miller is a horticultural expert at TheGreenPinky. She previously owned a landscaping business for 25 years and worked at a local garden center for 10 years. Read More