What Grow Lights are Best for Hydroponics? A Complete Guide

While many growers struggle with some of the many variables when running a hydroponic system, they can overcome these, and come to understand how things work. However, for newer growers, there is one area that can cause persistent problems, and seems to elude them how they can conquer it and fully understand it.

This is lighting, and it is one of the most crucial aspects of any hydroponic system. The thing is, there are so many lighting types available, and each set of plants can react slightly different to lighting if conditions aren’t exactly the same.

The hardest part for new growers is deciding which lighting system is the best. This can be difficult to understand because each lighting system offers very different characteristics than another. It isn’t a matter of giving plants any old light, it needs to be the correct sort of light, and knowing which lights can deliver this is half of what causes the problems.

There are plenty of lighting choices, so here we will run through each type to see how they operate, and what is unique about them.

It should be noted that when purchasing lights, apart from LED lighting systems, they are given a rating which is measured in lumens. These lumens bear little in relations to plants and are a scale that we, as humans use as a means of determining brightness. For plants, the main thing is the Kelvin rating which is a scale and relates to the different areas of the color spectrum.

A light might be bright to us, but to plants, the light may not be doing anything.

How Lighting is Measured

Before going through the various lighting types, it is good to see how light is measured, and what each bulb has to offer.

There are a few ways that light is measured, but some are almost obsolete, but still used in some things. Foot-candles or candle power is one such term, and this often relates to flashlights or spotlights that shine in millions or thousands of candle power.

Temperature is one of the primary terms you will see when growing in hydroponics and when looking for the ideal light. This temperature has nothing to do with heat output, but it is a reference to the natural color of the light produced.

When we see cool lights, these deliver light at the blue end of the spectrum while when we look at lights which are warm looking, these are providing light at the orange/ red end of the spectrum.

Lights can be measured by watt power, nanometers (nm), or Lumens most often. The watt power is the units of energy required to run the lighting, and it is the term most people are familiar with. When it comes to grow lights, these are often rated to the number of watts needed for each centimeter squared of the surface to be illuminated.

Lumens is a reflection of how bright a grow light is, and although used, these lumens are not actually a rating that does anything for the plants. The light required by plants is beyond the physically visible spectrum.

When light is measured in nanometers, this is actually the light we can see. This visible light falls in the range of 400 to 700 nm. When you compare this to the color spectrum, the warm or red end will be reading 730 nm, and at the other end in the color part of the spectrum (violet), this will be reading 400 nm.

Almost all grow lights fall in the range of 450 nm to 730 nm. These are the most crucial nm measures with one addition of 650 nm in the middle of the spectrum.

We all know that plants need to photosynthesize, and for plants to do this, there is the need for a light at the 450 nm and 650 nm levels. With these, plants can create the food it requires from the light available along with water and carbon dioxide. It is the green pigment where chlorophyll is produced.

When plants use the 650 nm and 730 nm ranges, this allows them to control their flowering through another pigment which is called phytochrome.

This is why the full spectrum of light is required at varying stages of a plants growth, and this is why it is crucial to have the best lights that allow growers to replicate this.

Here we will take a look at each lighting system, and see what they offer for plants, and hopefully, we can determine which are the best lights for hydroponics.

Fluorescent Grow Lights For Hydroponics

These lights have been around for years, and they are an economical bulb to run. One other main advantage is they run cool and can be placed very close to the top of plants with no fear of burning. However, this plus point is also highlighting one downside of these bulbs. The light they give out isn’t strong enough to penetrate past plants outer foliage or leaves.

One of the latest improvements is the introduction of the T5 bulb system, but there are a couple of things to know for this lighting type.

T5 Lighting Fixtures

With these, you can find more than a dozen variations in size. Knowing the dimensions for your growing area can be crucial so you will need to calculate growing space and then calculate your lighting needs.

There are usually two lengths that these bulbs can be found in, which are 2ft or 4ft in length. Along with this, some fixtures sizes can hold either 1, 2, 4, 6, 8 or 12 lighting tubes. This delivers lots of flexibility once you calculate your grow space. The rule of thumb is a small space with a few plants you can use a 2 or a 4ft light that has 1 or two bulbs. Larger areas and more plants, you will need a 4ft fixture with more bulbs.

T5 Bulbs

One of the largest draws toward T5 tubes is that they cover different color temperatures. Although it is hard to give an exact figure which meets different growers requirements. Choosing a bulb that delivers 6,500 Kelvin is a good starting point for plants in the growth phases. For flowering, bulbs that offer 3,000 Kelvin are more suitable.

There is also 3 outputs for T5 tubes, these are NO (Normal Output), HO (High Output), and VHO (Very High Output). To get the best of both, the HO (High Output) is a good recommendation. These are energy efficient while delivering plenty of good light, and are long-lasting.

T5 grow lights can be placed 6 -8 inches above your plants. If you have seedlings, or your plants are showing signs of dislike, raise this to 12 inches.

Pros

  • Cheaper than most other lights
  • The emitted light can cover larger areas than other lights
  • Versatile and long lasting

Cons

  • Not the best choice during vegetative growth stages
  • Not the most suitable for flowering stages

 

HID Lights for Hydroponic Systems

HID’s (High-Intensity Discharge Lights) are systems which come with much larger bulbs than other systems. These work by a gas being ignited inside the bulb. This is done by electrodes that sit close together, and when a current is passed through these, the gas becomes ignited.

This type of bulb is available in two varieties, but the third being a hybrid of the two.

  • MH – Metal Halide: These burn gas that produces lighting toward the bluer end of the lighting spectrum. This is beneficial for the vegetative stage of a plants growth cycle.
  • HPS – High-Pressure Sodium: This bulb type produces light that sits toward the red/ orange end of the spectrum and is much better for plants that have reached their flowering stage.

The problem with all HID bulbs is they need other components to run and be effective. These are as follows:

  • Ballast – this is what helps the bulb start when it is turned on, and it also helps to maintain the flow of electricity. These come in two forms and are a magnetic ballast that uses coils and a condenser to regulate power, and the second is the newer digital ballast options. These are more effective and cost-efficient when running.
  • Reflectors – these are, in the purest form a light steel hood which sits above the bulb to force light down to the plants.

HID’s lose their (Lumen) effectiveness by almost 70% once they have been used for a total of 10,000 hours or more. To put this in perspective, if you ran the lights for 14 hours per day, this is around 2-years. However, there are a lot of growers who monitor their lights closely and change them well before this period is up.

But, even with this need for changing on a regular basis, these are very effective bulbs. They deliver very active UV rays through the light that is given to plants, and with this comes some very productive photosynthesis.

Pros

  • Can be dimmed, so customizable light can be delivered
  • Digital ballast allows for all HID bulbs to be used
  • Deliver better usable light than T5’s

Cons

  • Can burn plants if placed too close
  • Require additional components to operate – ballast, reflectors
  • Bulbs loose effectiveness over time – require frequent changing

Led Lighting Fixtures

These lighting fixtures have been around for a little while, but they are still new in hydroponics for a good number of growers. Although they are still relatively expensive, they do come with numerous benefits over other lighting systems.

Luckily, as they gain more popularity, their prices will continue to fall. However, some manufacturers produce lights that deliver lower amounts of light. When looking to purchase, be sure the lights you look for are 2.0 micromoles per watt of energy as a minimum.

These cheaper LED systems aren’t enough to support flowering plants, so it is essential to do some homework beforehand. This can change depending on the type of plants being grown, but hopefully, these subpar systems will vanish when costs fall.

One final thing to note when looking to buying LED lighting systems is that many are sold as being all in one unit. In some cases, this isn’t the case, and there is a need for reflectors to be used with the LED lights.

Pros

  • Very energy efficient, and are among the cheapest light sources to run.
  • LED’s produce more light per watt of energy than both HID’s and fluorescents. But with some exceptions
  • The LED’s run much cooler, so there is considerably fewer chance plants will be burned
  • LED’s are very long lasting, and in many cases, it is the control unit which fails before the bulbs themselves
  • LED’s don’t need any ballast to operate and can be plugged directly into the mains socket
  • LED’s cover a wide range of the color spectrum and is adjustable so they can be tailored to your plant’s needs and stages of growth
  • LED’s are now known to be the easiest to use

Cons

  • At present, these lighting fixtures are more expensive than the alternatives
  • Some of the lighting systems throw out less light than other varieties of grow lights.
  • Some manufacturers produce lights which don’t have the power to support plants when they are in their flowering stages.

Alternative Grow Lights

Although these are the primary three lighting systems, and with good reason. They all have their benefits, but this still isn’t good enough for manufacturers. They keep on striving away to produce more efficient and cost-effective solutions.

Here are some of the alternative lighting systems you might be hearing of and seeing more of in the near future.

Induction Lighting

These are basically new versions of CFL’s (compact fluorescents). The way they operate though, is pretty technical. What they do is to ignite a gas compound that is generated by means of magnets. For this, there is no igniter, and everything happens inside a sealed tube.

Their light creation process produces less heat than it does light. This gives them a theoretical range of 100,000 hours which is way above any other system.

One problem they do have is, they can interfere with cell phones and Wi-Fi signals

Pros

  • Almost double the efficiency of other fluorescent lights
  • The theoretical lifespan of the usefulness of over 15 years
  • Cool running so they can be placed closer to the tops of crops
  • Instant on compared to lights that require a warm-up period

Cons

  • Noisy in operation
  • Too new, so still very expensive
  • Still not as efficient as HPS or LED’s

Double Ended Lighting

DE (Double-ended lighting) is relatively new and is a form of HID lighting system. It follows the HPS bulbs, but rather than being a single ballast socket. It is a double ended tube which connects to the ballast at both ends. While there are a few similarities to HPS, they do have key benefits and also downsides.

Pros

  • DE lighting has a longer lifespan than their single socket counterparts.
  • More efficient – these bulbs can retain as much as 90% of their efficiency compared to previous bulbs over the same amount of hours usage.
  • Thin tubes allow for closer plant placement compared to single ended bulbs

Cons

  • Although they can be placed closer to plants, they do run hotter and can cause leaves to burn
  • Direct airflow reduces the efficiency of the lamp while in operation

Sulphur Plasma

These bulbs burn gas at very high temperatures, and in effect, they are replicating the sun. At present, all the information is still in developers hands because these bulbs are still new and in testing.

At present, there are only pros and cons to be shared, but no doubt, if these are found to be beneficial, then every grower will quickly hear about them.

Pros

  • The bulb has the potential to create almost natural light because the spectrum of generated light is close to that of the sun.
  • If successful, these can be the best option for larger grow rooms, or where bulbs can’t be placed close to crops.
  • The lifespan is expected to be 3X or 4X the length of other forms of traditional hydroponic lighting systems.

Cons

  • Not suitable for smaller grow rooms because they burn so hot
  • Fixtures are large and bulky
  • Very expensive

Conclusion

As you can see, not all grow lights are created the same. Each comes with its own benefits, and also its own unique downsides.

On top of this, is the fact that all grow rooms are very different, so there are countless other variables growers need to consider. Lighting is only one part of this puzzle, but it is evident, no one lighting system is perfect.

Growers need to understand all of their plant’s requirements, and also what they want from their plants. When they know this, they can put things in place, and choose the best lighting system that their budget allows. Even then the choice may not be so simple, but at least growers will know the options they have, and which lighting systems are most suitable for them.

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About the Author

Oscar Stephens
Oscar Stephens
I am a gardening and tech enthusiast! Stumbling across the world of Hydroponics, Aquaponics and Aeroponics by accident I've decided to create TheHydroponicsPlanet to put all of the best information I can find in one easy to navigate place. I'll continue to add more content as I discover new things!