6500k Lighting question

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Fish-n-beer-guy

Aquarium Advice Apprentice
Joined
Oct 26, 2011
Messages
24
Location
Fremont, CA
So I've heard a bulb fir planted aquarium should be 6500k. True or false? If true does it matter if the bulb is specific for plant growth or can I find a bulb at my local hardware store that us 6500k?
 
no expert in planted tanks, only had 1 for 2 months myself but 6500 T5 is a good bulb for plants. I got my lighting from Ebay but only because my local stores didnt have any T5 6500s.
 
The Bulbs ive got in my Fixture are 6500s T5Ho, and my plants are doing great. Its coming soon to the time to change the bulbs out, so im gonna replace with a 6500 and a Pink plant bulb ive seen and give that a try. But honestly im sure it wont make much of a diffrence if its 6500 or if its 10k
 
The colour temperature alone will not tell you if a lamp will be good for plant growth. For good plant growth you need some specific wavelengths of light in the red and blue spectrum. Typically, lamps in the 5000K to 6500K range have these at least to some degree. not all lamps of a given temperature will be equal. If you compare Colour Rendition Index (CRI) numbers they will range from the low 80s to the high 90s. A lamp with a high CRI will more likely have all the wavelengths covered.
My personal preference for plants is for 5000K tubes, which to me make the plants look better, and grow better, even with a lower CRI. the reality is that plants will grow under a variety of lamps, but will do better under some, which in my experience is the more natural looking ones.
 
K stands for Kelvin, which is the color temperature of the bulb. A plant can use light ranging anywhere from 5,000-10,000K in photosynthesis. So what you've heard is partially true. It could also be anything else in the range.
 
K stands for Kelvin, which is the color temperature of the bulb. A plant can use light ranging anywhere from 5,000-10,000K in photosynthesis. So what you've heard is partially true. It could also be anything else in the range.

BillD already explained why we don't use Kelvin as a true indicator for plant use. You are going to confuse people.

Plants don't use light in any particular Kelvin range. They use light in the 350 to 700nm range. You have to look at the lights spectrum, not it's Kelvin rating.
 
BillD already explained why we don't use Kelvin as a true indicator for plant use. You are going to confuse people.

Plants don't use light in any particular Kelvin range. They use light in the 350 to 700nm range. You have to look at the lights spectrum, not it's Kelvin rating.

The problem is, a lot of CFLs don't list the spectrum. With CFLs, unless it's an aquarium specific one, you have to go by color temp. Since they were talking about bulbs from the hardware store, I'm assuming that they are T8s, T12s or CFLs. None of these typically have the spectrum listed, but only the color temp.
 
Look for
Full Spectrum
Warm Daylight
6,500K or somewhere near that is fine.
May or may not mention plants.
Wattage will depend on the size of your aquarium.

For my low light 10g I use two 10watt CFLs
ZooMed UltraSun 6,500K Mini CFLs from Amazon. Grows a LOT of plants.
 
Thanks for the replies! Where can I find the "nm" rating on bulbs? All I ever see is the Kelvin and some say full spectrum.
 
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