light "K" values how important for plants

[mrmike]

I heard that around 6500k is best for plants. But i have read numerous articles where people run the typical marine lights like a 18000k and an actinic bulb to grow. So what gives, will the 18k and act. bulbs grow plants also. Which is the best bulbs to run. I have 4 flourescent tubes running 2 nutrigrow bulbs, and two all-glass aquarium bulbs, and thought about running an actnic bulb. But will that hurt plant growth? Just wondering best for plants??

 

[james595]

Actinic bulbs won't provide much for the plants. They are really only useful for making colors pop out. A lower K value will provide the best photosynthesis. Look for peaks in the output around 700 nm. The only downside is that the "grow" bulbs are not very visually appealing.

 

[ed seeley]

Plants don't care about K values. All they need is enough light to give them the energy they need to activate the photosynthetic reaction. Very blue lighting is not the best for this but aside from that you should simply pick the colour of lighting you prefer! Personally that is daylight bulbs of around 8,000K for my eyes. If I were you I'd try and swap the bulbs you have for ones with daylight K values but you don't need these grolux type of bulbs to grow plants.

 

[dw1305]

K values

Hi all,
Ed is right, a lot of what is written about aquarium lighting is written by people who have no idea what they are talking about. As a very basic rule of thumb lights of 5000 - 10,000K are suitable for growing plants.

Any tri-phosphor natural daylight bulb (bought of the shelf for £5) will make your plant grow, just as well as the most expensive offering by Hagen etc.
I like the T5 lights, they are electronically ballasted and reasonably efficient, but electronically ballasted T8 lamps are absolutely fine.

For various reasons measuring the actual effectiveness of any lamp is not straightforward, and therefore lamps are rated in lumens, watts, K value & by CRI, none of these are of any relevance to the growing plant. The Kelvin values (K) are a reference based on the light emission of Iron (Fe) at various temperature (in degrees Kelvin), they go from "low" K values "red hot" through "white hot" etc. as the temperature increases.

Photosynthetically active radiation (PAR) is the measure of lamp output (radiance per watt) in the spectrum that is actually useful to the plants. However, this data is only available for a small number of lamp models.

Irradiance at the plants can be measured directly, as photosynthetic photon flux density (PPFD). This is measured in Einsteins (E), One Einstein is one mole of photons, regardless of wavelength. Irradiance levels on the surface of the earth occur on the scale of micro-Einsteins, however the meters are not cheap or widely available.

cheers Darrel

 

[pjrichar]

light needed

I have a 55 gal i want to start to plant..

What are your suggestions for lighting that arent outrageous expensive.

t5?
HO t5? one bulb or two
etc?
any help is appreciated

Patrick

 

[dw1305]

Under cabinet lights

Hi Patrick,
I'm not sure what the length a 55 gallon is? is it long and thin? 48 x 12 x 21?

If it is thin but relatively deep I'd probably go for the HO T5's, although either electronically ballasted T8's or ordinary T5's will do.

I think you only need 1 tube if you can get 4' 54W T5HO. Four foot is the lighting standard so you usually get more watts per $ that way anyway.
You might find 2 x 54W gives you too much light.

T5 link lights are usually 2', but they are cheap to buy and you can daisy chain up to 10 together from one plug.

Have a look on Ebay for hydroponic growlights, "link lights" or "under cabinet" lights.

This sort of thing, (these were the first links on the google search rather than a recommendation for the company)

<http://www.plantlightinghydroponics.com/t5-sun-blaze-strip-lights-c-321_563.html>

cheers Darrel