LED Planted Aquarium Lighting: Part 2

In the first part of the series on LED lighting in the planted aquarium, I discussed whether or not LED lighting would work for growing live freshwater plants, and if so, why hasn't anyone made a fixture you can buy yet that isn't $1,000+. Now if you're either brave and the DIY type or have some deep pockets and want to give LED lighting a try, but need that extra justification to give you a push, here are some quick pros and cons of LED lighting in the planted aquarium:

Pros

First, the pros, and there are lots of them. You'll find that most come with some caveats though.

The first one that jumps into many people's minds is their lower energy consumption. Most high powered LEDs (the sort you use for growing plants) only use 2-4 watts of electricity and pump out anywhere from 100 to 300 lumens (for comparison a 70 Watt metal halide bulb produces around 5000-6000 lumens). So depending on the size of the aquarium and the quality of LEDs that you buy, you could see a slight drop in power consumption. However, this drop is not huge, contrary to popular belief. If power saving is your main qualification, I'd lean more towards T5 fluorescents (these usually put out about 2000 lumens for a 24 watt bulb).

Another benefit of using LEDs is that they don't emit quite as much heat as high temperature metal halide lamps do. Again, there have been misconceptions about LEDs thinking that they don't create much heat at all. Regular low powered LED's don't really, but high output LEDs do. Substantial heat. So much that you need heat sinks and fans to keep them cool. Granted, they don't get quite as hot as metal halide lamps, but they require more robust cooling systems than any fluorescent fixtures. And heat is critical determinant to how long an LED lasts, which brings me to my next point.

LEDs last a long, long time if they are treated right. This is a huge benefit over fluorescent bulbs that dim or shift their spectrum and need to be replaced every 8-12 months. I just shelled out $70 for two new bulbs for my 2 x 96 Watt CF fixture and will need to do so every year. LEDs should last the life of your aquarium (or at least 50,000-100,00 hours) provided their temperatures are controlled. You see, the lifespan of an LED is directly linked to its operating temperature. The hotter they run, the sooner they burn out. This is why heat sinks and cooling fans are necessary.

Another big difference between bulb type lighting (fluorescent and metal halide) and LEDs is that LEDs do not require fancy reflectors. They emit all of their light in one direction via highly efficient internal reflectors, and therefore eliminate inefficiency due to light bouncing off the reflector and back into the bulb or off into the room instead of into the tank. If you are putting together your own DIY fixture, this means that buying a reflector isn't always necessary (depending on your LEDs) and can save on costs and space a bit.

LEDs are small, and produce a lot of light in a very small space. Only metal halides pack as much light in a small space. Try lighting a nano tank to levels that qualify as high light with a flourescent and you'll see why this is awesome. In order to be high output, fluorescent bulbs need length...and that won't work on a tiny tank (except spiral CF bulbs). You can't really put a 70W metal halide over a nano tank either, unless you're planning on boiling some water. This small space footprint also brings up another benefit of LEDs, although it is purely aesthetic.

LEDs produce that ever-illusive shimmer effect. You know, the glimmer in the water that sun casts that just looks so awesome. Until LEDs, only metal halides could do that, since they were the only other point-source (meaning all light is emitted from a small area) fixtures available to planted aquarium keepers. As stated before, metal halides don't really work over smaller tanks for obvious reasons. Now those of you with smaller tanks can bask in the shimmering glory as well!

Finally, LEDs can produce exactly the wavelength of light needed by plants. There are very specific wavelenghts that plants use for photosynthesis, and if you didn't care much about how the planted tank looked to the human eye, you could buy LEDs that only emitted these wavelenghts. Of course, that wouldn't look very pretty...or natural, since it would be only red and blue light. But the point is you can control the wavelengths present in your lighting, instead of a wide range produced by other types of lights.

Cons

There are a few cons to LED fixtures, the largest being cost. LEDs are just too expensive still to use for large aquariums and provide the light necessary for plant growth. At approximately $10 an LED, not including controllers and cooling systems, the costs quickly add up. It's easy to see how commercially produced fixtures like this one sell for $700-$1000. Eventually, the costs will come down as high output LEDs are put into more and more applications, but for now, we're stuck with paying for this new technology.

Another downside of LEDs is that they still produce a large amount of heat. They aren't the ideal solution for aquariums that are highly sensitive to heat, or in hot climates where keeping the tank cool can mean running a chiller or blasting the air conditioning. They don't quite reach the temperatures of metal halides though.

And finally, considering there are only a few large commercially produced LED fixtures available, if you want to light a smaller tank, or if you can't afford the large fixtures, you'll probably have to make your own using parts bought online. This requires soldering, wiring, and constructing a housing that can effectively cool the LEDs. It's no small undertaking, but it is possible and fairly straightforward.

Final verdict: If you have a small tank (too small for most fluorescent tubes and metal halides), some electrical DIY experience, and don't mind putting together a cooling system, a small LED fixture is probably your best option for high output lighting.

LED Planted Aquarium Lighting: Part 1

Power compact (PC) fluorescents, T5 fluorescents, and metal halides (MH) dominate the planted tank hobby. All three are more than adequate for growing plants and all three are a step up from incandescent lighting (which probably won't grow you much more than algae) and regular fluorescents. But in the past decade, a new aquarium lighting technology has been making technological advances that could soon put it above your aquarium. Light emitting diodes (or LEDs) promise a lot of light in a tiny space and all using less energy. So what's the deal with LEDs? Can they grow plants? Are they cheaper/better than the alternatives? Can I buy an LED aquarium fixture?

LEDs are seen as the future of aquarium lighting. These aren't the same dim LEDs you'll find in moonlights or household electronics (usually 1 watt or less). The best those can do is "supplemental" lighting. We're talking high powered LEDs, LEDs so bright you can't safely look at them (typically 3 or 4 watts). These LEDs are actually excellent for growing live aquarium plants. Unlike fluorescents, which produce light at a whole handful of wavelengths (some of which may not be useful to plants and actually can cause cyanobacteria and algae to thrive), LEDs can be much more precise and target the exact wavelength of light that plants need, maximizing their efficiency. Therefore, the traditional (and pretty inaccurate) watts per gallon measure can't really be applied. You can get the same results with a much lower wattage of LEDs, saving money on electric bills.

But why haven't we seen LED lighting fixtures burst onto the planted aquarium scene if they'd be ideal for growing aquarium plants? Well, primarily, the reason is cost. You can get LED fixtures for growing live plants, but they cost an arm and a leg. And another leg. The 60 inch Solaris LED fixture (now discontinued, but one of the first mainstream LED aquarium fixtures) used to retail for around $3,000. Prices have been coming down a lot lately, but they're still mainly only for the deep pocketed aquarium keeper. If you can afford them though, they seem well worth it. Check out the new epro LumenAqua and the product demo video (below) on YouTube. Go ahead, watch it, it's worth it. I'll wait.



Chances are, after watching that, you either bought one (and I'm extremely jealous), or checked under your sofa's cushions, hoping to find a few hundred dollars. We'd all love to have something like that one day right? So why are they so expensive? Mainly because the high intensity aquarium lighting market is so small, and because the technology is still relatively new. It's also advancing at light speed (sorry, pun intended). So for a manufacturer to produce a product that makes a profit with such low volume, it's gotta be expensive. Until the hobby gets much larger (which it will, but it'll take time), or the price of the LEDs drops (which it is), these units will be fairly expensive.

Then, there are other issues, like a recent lawsuit that disputes key patents used in LED fixtures for aquariums. These kinds of legal issues can take years to resolve, and in the meantime, the technology is in limbo. While some manufacturers of LED fixtures may be waiting for the lawsuit to blow over, DIY hobbyists are not.

Several DIYers have made their own LED lighting fixtures for the planted aquarium using parts purchased online. It's relatively easy, and can be a cheap alternative. However, at anywhere from $4-10 an LED, plus costs for heat dissipation fans and heat sinks, and wiring, and controllers, the larger the aquarium the less feasible this becomes. Right now, DIY LED fixtures for aquariums are best suited for smaller aquariums, where PC, T5, or MH just won't work.

So if you're a handy DIY type with a smaller tank or able to spend $1000 on a light fixture, LEDs will work just fine in a planted aquarium. Just be sure you're getting high powered LEDs meant to replace aquarium lighting, and not "supplemental" LED fixtures.

But the question remains: Are LEDs right for you? In the next part of the series on LEDs, I'll discuss the pros and cons of LEDs as aquarium lighting to help you better decide whether or not they're right for your aquarium.

Understanding Full Spectrum Aquarium Lighting

Picking the right lighting for your planted aquarium can be intimidating and confusing. There are so many options to choose from, and so many ways to measure these options. The first step to understanding full spectrum aquarium lighting is to understand what type light your plants need, and what the measurements mean.

Color temperature, measured in Kelvins, is often the easiest measure to find, after wattage. It is a measure of the overall color of the light as it appears to the human eye. Lower color temperatures appear reddish while higher temperatures appear bluish with white in the middle of the range. Often, a temperature between 5000K and 10,000K is recommended for a planted aquarium. However, two bulbs with the same color temperature may in fact be emitting very different light, some more useful to plants than others. This has to do with the different wavelengths of light, and explains why relying on color temperature alone can be misleading.

Visible light is made up of many different wavelengths, mixed together. It's the absorption or reflection of particular wavelengths that produce colors. Plants require certain wavelengths of light to carry out photosynthesis using chlorophyll. The light that chlorophyll absorbs is used to power photosynthesis. By examining the wavelengths of light absorbed by chlorophyll, we can begin to understand the needs of our aquatic plants.

As shown above, plants need the majority of the light to be around 400-450nm and 650-675nm (or blue and red light). The blue light is used for leaf growth, and promotes bushy, compact growth, while red light is mainly used for flowering and strong stems. They reflect most green light, thus explaining why leaves are green.

Armed with this information, we know that any aquarium light will need to produce large amounts of blue and red light. Most bulb manufacturers include the spectral output graph of their products on or in the packaging. Examine this output graph and try to find a bulb that matches up with the spectral absorption graph for chlorophyll. The closer the match, the better the bulb will be for your plants. For example, the following graph is for a GE 9325K bulb.

The bulb matches up fairly well, although the spike at 600nm is not really red enough (650-675nm) for a plant to fully benefit. The blue light spike is however beneficial, and the spike in greenish-yellow light will make the bulb look bright to the human eye.

Although you may not notice a major difference between bulbs, a mix between a color temperature that you like and a spectral output that your plants like will help create healthier plants and a healthier aquarium.

For more in-depth information on the science of full spectrum aquarium lighting, check out this discussion of aquarium lighting science and photosynthesis, or this aquarium light bulb comparison study. For more information on lighting metrics, check out this page on Kelvin, nanometers, PAR, and CRI.