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.

Beginner's Guide to Planted Aquarium Supplies and Equipment

I've decided to try to take a stab at an idea suggested by a visitor and create a shopping list of essential supplies and equipment needed to start and maintain a planted aquarium. As I thought about exactly what was needed, I realized that the supplies and equipment needed depends greatly on one thing: the amount of light in the aquarium. As I've mentioned before, the light in the aquarium is the engine driving the mini-ecosystem. The more light you have, the more equipment and supplies you'll need to keep that ecosystem running smoothly.

All planted aquariums need light, obviously. So the number one item on the list is a light. Lights come in all shapes and sizes and powers (see a guide to making your own cheap high powered lights). How much light you have on your aquarium will determine the rest of the list.

For low light aquariums (1.5-2 watts per gallon unless you have a very small or very large aquarium, then read this post on light in the aquarium) the equipment and supplies needed are minimal. Most are required for any aquarium:

• Light (at least 1.5 watts per gallon)
• Filter (biological and mechanical, the plants will take care of chemical)
• Heater
• Substrate (can be plain gravel, though not ideal)

That's really all you need. In a bare-bones setup like this, you won't grow fancy plants or even grow things particularly well, but low light plants should survive just fine. As you can see, as long as you have an aquarium with fish already, you will likely only need a better light.

For medium light aquariums (2-3 watts per gallon) you will start to need to supplement your plants for them to grow healthy:

• Trace element fertilizer (such as Seachem Flourish or CSM+B)

For high light aquariums (3+ watts per gallon) you must add the following items otherwise your aquarium will quickly become an algae farm:

• CO2 system or Flourish Excel
• Nitrogen, potassium, and phosphorous fertilizers.

As you increase the amount of light on your aquarium, you increase the demands in terms of fertilizers. Once you get into the high light category, you really need to add fertilizers otherwise the plants will suffer and algae will take over.

It is important to remember, if you add fertilizers or CO2 to a low light aquarium in the proper amounts, you will still see an improvement in growth. There's no rule that says that low light aquariums shouldn't have CO2 or fertilizers. You just have to remember that plants aren't going to grow as quickly and won't need as much fertilization as plants in a high light tank.

As a beginner, I'd recommend starting out with low light and working your way up. Diving straight into a high light aquarium can lead to things quickly spiralling out of control. That, and it's fairly easy to upgrade your aquarium as you go.

Amano's Ideal Light Levels Revealed

I've just stumbled upon this very interesting article on what the ideal level of light for an aquarium is according to the aquascapes of Takashi Amano. World-renowned aquascaper and founder of the Aqua Design Amano (ADA) contest and sponsoring company, Amano has published several books of his aquascapes and given light levels along with almost every aquascape. Using this information, John Fitch has not only discovered that Amano uses more light per gallon on smaller tanks, but has also developed a calculator to determine, using the data from Amano's tanks, roughly what light level Amano would be likely use on your aquarium. The calculator can be found in the article, which is called "Lighting as a Function of Tank Size in the Aquaria of Takashi Amano."

This is further evidence against the Watts per Gallon rule, which was always just a rough guide. In other words, 40 watts over a 10 gallon tank may seem like a lot of light (4WPG), but in fact, it should have closer to 65 watts. The reason for this is due to surface area, but exactly why I haven't quite gotten a handle on yet, so I'll do more research and report back when I have a better idea. All I know is that smaller tanks demand more light per volume and larger tanks demand less. The WPG rule holds for the most part in medium sized tanks (about 29 gallons to 55 gallons), but below and above that, it's better to go by something like this tool, or do your own calculations using surface area (-gulp-). Personally, I like the tool...