One of the most common questions we get asked is “What light should I get for my planted aquarium?” The short answer is that it depends. To help you get started on your planted tank journey, let’s talk about three different lighting parameters and what they mean for beginner hobbyists.
If you’ve ever looked at the lighting in a cozy coffee shop versus a sterile hospital, you know that “white” lights all vary in color temperature, which is measured in units of Kelvin (K). A soft, warm reading light that gives everything a yellowish glow may have a rating of 2700K, whereas a cool white light with a bluish tint may be labeled as 10,000K.
To be honest, color spectrum doesn’t matter that much when it comes to growing aquarium plants because they can thrive under a wide range of Kelvin. It mostly comes down to human preference because we don’t want to look at aquarium lights that are too red or blue. Many hobbyists like to use a neutral white light around 6500 to 7000K because it’s said to best simulate natural daylight. Simply speaking, you can choose a light with just about any color spectrum as long as it’s not too blue (such as those used for raising saltwater corals).
Plants can grow under a wide spectrum of lights, so pick a color temperature that you feel makes your plants and fish look the best.
How bright of a light should you get? First off, it depends on what kind of aquarium plants you want to grow. Low lights (or low-intensity lights) can grow anubias, cryptocoryne (or crypts), ferns, and other undemanding plants. Medium lights are good for stem plants and most other species except for demanding carpeting plants. High lights can grow virtually anything, but often require carbon dioxide (CO2) injection in order to keep up with the fast plant growth and to minimize algae blooms. Because of the complexities that come with high light planted aquariums, we recommend that most people start with growing low light plants since they’re some of the hardiest, most beginner-friendly species.
The next question is “What is considered low light versus high light?” The intensity of plant growing lights is often measured as PAR (or Photosynthetically Active Radiation). However, most manufacturers don’t publish their PAR numbers because this rating differs drastically depending on how deep the aquarium is. A tall tank requires a very strong light to illuminate the bottom of the tank where the plants are growing, whereas a short tank does not. A Finnex Stingray LED light would be considered low light on an aquarium that’s 21 inches tall, but that same light on a 12-inch-tall tank could easily grow medium light plants.
You can use almost any type or brand of light to grow plants as long as you have enough light intensity, but we highly recommend getting an LED light – rather than fluorescent, compact fluorescent (CF), or other light technology. Nowadays most planted tank lights use LEDs because they can produce high brightness with lower power consumption and they do not need to be replaced very often. Plus, some LED aquarium lights are dimmable, allowing you to control the light intensity in case you want to use them for different tanks that have different PAR requirements.
The intensity of a light varies a lot depending on where you are measuring it in the aquarium.
The final category to consider is how far the light spreads or disperses. Most aquarium lights have a good 1-foot light spread directly below them, meaning that plants outside of that window won’t get as much light and potentially won’t grow as well. On the other hand, a shop light has a huge light spread because it’s designed to light an entire room. (Just be aware that the color spectrum on a shop light may not show off the colors on your plants and fish as well.)
Depending on the size of your aquarium and the spread of your light, you may need multiple lamps to properly grow plants in all parts of the tank.
So, if your aquarium is 18 to 24 inches wide, you may need to buy two aquarium lights or use one cheap shop light. Also, some manufacturers like Fluval sell higher quality aquarium lights that boast a 120-degree light spread, which would cover more area than a generic brand light.
Now that you know the basics of planted tank lighting, you know that the answer isn’t that simple. There are several questions you need to answer for yourself:
As you’re first getting into planted tanks, there’s nothing wrong with choosing a cost-effective light that does well at growing low light plants. But if you have some birthday money saved up, it may be worth considering the higher priced options. These higher quality lights tend to last much longer and have extended warranties backed by the manufacturers. They also come with interesting features, like the ability to adjust the color spectrum, dim the intensity, and imitate the gradual sunrises and sunsets seen in nature.
For more information, check out our LED Aquarium Lighting Guide for concrete suggestions on which lights to get based on your aquarium size.