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Discussion Starter · #1 · (Edited)
Ok i hope gets me a solid answer without sparking a massive debate. What Kelvin rating on the bulbs should i be running, i have looked at bulbs on a number of sites and they have 3000k,4000k,4100k,5000k,5500k,6000k,6500k, 6700k,8700k,9000k, 10,000k, 12,000k,14,000 and other odd numbers like 9825k I have even seen 20,000k bulbs but those were MH. There are also 50/50 bulbs,Actinic, Fiji Purple bulbs, and the Weird pink "Plant Grow Bulbs" All this is a bit much for the Average Joe to sort through and figure out.

Here is some info the "website" lists not sure on accuracy,6500K for rooting and vegetative growth stages.3000K for flowering and fruiting growth stages.4100K spectrum for rooting and vegetative growth stages.5000K for rooting and vegetative growth stages. It is just confusing, does this mean i need one of each of these bulbs?? Or will a 6500k bulb do everything that a 3000k,4100k,and 5000k bulb will do?

I have a 10,000k bulb right now.

Is there an "Ideal" K rating for a planted tank,if so what is it?

Are 10,000k bulbs good for planted tanks?

So What K rating is best Avoided in a planted tank?

If it should be a mixture What K ratings are Best?

Please Answer the above assumeing CO2,Ferts, Etc AND for a low tech no Co2,no fert tank.

I have often wondered if maybe my 10,000 wasn't part of why i have problems with plants, because the mosses i have in my smaller tanks under a 6500k bulb look far better than the moss under the 10,000k bulb.
Thanks in advance!
 

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K ratings are a function of the overall spectral output of a bulb. Plants particularly like output in the 400 & 700nm ranges. Such output is generally abundant in almost any bulb that lies in the 6500K - 10,000K range although there are a few 10,000K bulbs that are heavily weighted in the lower wavelengths (blue end of the spectrum), making them inappropriate for plants.

That said, we move on to CRI (color rendering index). Unfortunately, CRI is not always readily available for every bulb. The higher a CRI value (can be from 1 to 100, in theory), the more like sunlight it is in appearance.

The ideal plant bulb would then have lots of output in the plant friendly areas of the spectrum while having an eyepleasingly high CRI. Some plant friendly bulbs are quite pink or purple, so they may be in the 6500-10,000K range but have a low CRI (<80). The 10,000K bulbs that are not plant friendly also tend to have low CRI because of all of the low wavelength light they put out (they look blue and are designed for corals - CRIs can actually get down into the 60s for these).

Now it is up to you to decide if the mosses in the one tank look better because of the CRI or because your 10,000K bulbs are not so plant friendly...
 

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Discussion Starter · #3 ·
K ratings are a function of the overall spectral output of a bulb. Plants particularly like output in the 400 & 700nm ranges. Such output is generally abundant in almost any bulb that lies in the 6500K - 10,000K range although there are a few 10,000K bulbs that are heavily weighted in the lower wavelengths (blue end of the spectrum), making them inappropriate for plants.

That said, we move on to CRI (color rendering index). Unfortunately, CRI is not always readily available for every bulb. The higher a CRI value (can be from 1 to 100, in theory), the more like sunlight it is in appearance.

The ideal plant bulb would then have lots of output in the plant friendly areas of the spectrum while having an eyepleasingly high CRI. Some plant friendly bulbs are quite pink or purple, so they may be in the 6500-10,000K range but have a low CRI (<80). The 10,000K bulbs that are not plant friendly also tend to have low CRI because of all of the low wavelength light they put out (they look blue and are designed for corals - CRIs can actually get down into the 60s for these).

Now it is up to you to decide if the mosses in the one tank look better because of the CRI or because your 10,000K bulbs are not so plant friendly...
Well i cant find the CRI on the bulb i have all i keep finding is lumens-per-watt (LPW) 95 LPW up to 105 LPW, but i cant guess that it is that great its the bulb that came free with the light fixture its a Currant USA bulb.

i have an email into currant to find out though.
 

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You can have two bulbs with the same kelvin rating yet have drastically different spectral outputs and intensity and CRI. Not all bulbs are the same.
 
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