Jake’s Planted Aquarium Pages

Ok, let’s destroy some of the mystery involved with lighting and different terminology. I won’t go all egg-headed on you, no worries. This isn’t lighting school, so if you want more information, feel free to google.

CRI - Color Rendering Index - The measure of the ability of a light source to reproduce the colors of various objects being lit by the source. The scale goes from 0 to 100, with 100 being the best. Not terribly significant to plants, but it is significant to your eyeballs. The higher the CRI on a bulb, the more vibrant and “real” the colors seem on what that bulb illuminates. We want to enjoy our tanks, and it’s easier to do so when that red plant in your tank looks like the red it’s supposed to.

“K” , as in “1000k bulb” - Refers to the actual color of the light the bulb gives, as compared to blah, blah, blah, measured in degrees, blah, blah, blah. Whatever. Anyhow, how it pertains to us is, again, to our eyeballs. Typically people use bulbs that are anywhere from 4500k to 10000k for growing plants. The lower the “K”, the more yellow the light appears. 4500k might appear as a dull yellow, while 6500-6700k looks to be a good midday sun. 10000k might look like a bright, crisp white light. All of these will grow plants just fine and you can mix and match to acheive the desired affect. My personal favorites are 6700k and 9325k. Based on the K (kelvin) rating, the 9325k bulbs are “supposed” to look blue to me, but whatever… I think they look pinkish.

Lumens- a measure of the total “amount” of visible light emitted. The higher the lumens, the “brighter” or more “intense” the light looks. Human perception weighs in on this measure , so it is not a “true” measure of plant growing capability.

WPG - Watts Per Gallon - An overall calculation of wattage of bulbs over a tank divided by gallons in tank, meant to give a person a basic tool or guideline to help in determining what plants they can grow and what the nutritional needs of the plants will be accordingly.

Watt - one joule of energy per second . For us, it’s a measurement of how much energy our light fixture is sucking up.

Lux - a measure of the intensity of light , but human perception weighs into the measure as well. This is why it is not a “true” measure of plant growing capability.

Spectrum - without boring myself or you, light has different wavelengths which are expressed in certain colors. It’s the pretty , colorful chart on the box the fluorescent tube is in at the pet store. Wide- spectrum means that the light will put out at least a little bit of all the colors in the spectrum. Thanks to Issac Newton, the colors he named in the spectrum are red, orange, yellow, green, blue, indigo, and violet. People though indigo sucked as its own color and should be considered just a shade of violet, so it’s not often referred to. Plants are supposed to like red and blue the most, and many bulbs claim to “spike” or put off a lot of these colors, but who knows if they do or not.

PAR -  Photosynthetically Active Radiation - This measure designates the spectral range of solar light from 400 to 700 nanometers that is useful to terrestrial plants in the process of photosynthesis. A PAR meter starts at $300+ though. If a person had to chose a method for determining what plants they could grow based on the lighting they have, or when deciding what lighting works best for growing plants, this is (arguably) what they would measure.

The codes on some fluorescent lights: For example, F15T8 .

F##T## = F stands for “fluorescent” , the next numbers for wattage ( or length in inches for very long bulbs), T for “tubular” which describes the bulb, and the next number for diameter in 1/8’s of an inch.

SO then, a fluorescent bulb that says “F15T8″ is a fluorescent tube that is 15 watts and 1″ in diameter.
HO or VHO ( high output or very high output) bulbs might go something like ” F##T12HO ” and “F##T12VHO” respectively, the ## being the wattage or length.

Bent tubes might say something on it like “FB##T##” ( fill in the #’s), with the extra “B” standing for “bent”.

VHO - Very high output, referring to the output of a fluorescent tube.

HO - High Output, typically referring to the output of a fluorescent tube.

ODNO - Over Driven Normal Output, typically referring to fluorescent bulb that is intentionally wired with an over powered ballast. Typically the companies which make fluorescent tubes under-rate their tubes because they are meant to last a long time and run at a cooler temperature. By overdriving the bulb(tube), you are essentially making the light more intense, run at a higher temperature, and last for a shorter duration. You have to make this kind of fixture yourself, and they are not considered 100% safe, depending on your wiring skills.

Restrike - Not really a “technical” term, it is something to be avoided in excess. It is basically when the light from your tube/bulb is reflected back to the tube/bulb without ever having reached the aquarium. Typically there will be at least some restrike, such as with a fluorescent tube’s light hitting the reflector and then hitting the tube again, but with some setups you tend to have a lot more of this than with others. Those spiral screw-in mini compact fluorescent bulbs, for example, that so many seem to be using in smaller tanks, have a lot of restrike due to the physical characteristics of the bulb. Take a look at a picture of one here, and then imagine it laying on its side above a tank. The bulb twists around, and that is fine for lighting a hallway or something, but imagine how much of that light from the “curls” on top is actually going to make it into the tank. A lot of it will just hit the bulb “curls” below it. Some will hit the reflector above it , (the reflecting surface in your fixture) , and then bounce back and still be blocked anyway by the bulb itself. That is a lot of restrike.

In a linear bulb, like a T5 fluorescent tube, the long, skinny physical characteristics of the bulb make it so the bulb is less in the way of the light coming from itself. Therefore, more light actually gets into the tank and that means more light for the plants. If mini power compact bulbs are to be used, the below picture is the type you want. Please forgive it’s old appearance as it’s been in use for quite awhile. I purchase these in the fish department of Walmart for around $5 each. As much as I hate Walmart, you gotta do what ya’ gotta do.

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