UnknownK vs. 8500K?

[Aquarius0015]

I didn't get any replies to this question in my other thread, so now it gets its own, and hopefully more people will notice it.

I have been searching all over for a 15" T8 fluorescent light bulb. All the ones I have found are 14 watts, which seems standard. I have been told to look for 6500-6700K.

Now, there are a few brands to choose from on BigAl's (best selection I could find), but most of the brands do not give a value for K, they just state in general terms that their bulb is good for fish and plants. The only one with a K value was a 8500K. Is it better to go for the mystery K bulbs or the one with the known K value, even if it is higher than what I want?

[Captain Hook]

How about some bulb names or at least who they are made by.

[Aquarius0015]

Here is the 8500K bulb:
http://www.bigalsonline.com/catalog/product.xml?product_id=23607;category_id=1849

"EMISSION SPECTRUM CLOSELY MATCHES ADSORPTION CURVE OF CHLOROPHYLL-A ,8500K HIGH INTENSITY LAMP WITH PEAKS EMISSIONS IN THE BLUE AND RED REGIONS TO MAXIMIZE THE PHOTO BIOLOGICAL PROCESS IN PLANTS."

Aqua-Glo Fluorescent Lamp:
http://www.bigalsonline.com/catalog/product.xml?product_id=23549;category_id=1849

Power Glo Fluorescent Lamp:
http://www.bigalsonline.com/catalog/product.xml?product_id=23691;category_id=1849

Flora-Glo Fluorescent Lamp:
http://www.bigalsonline.com/catalog/product.xml?product_id=23621;category_id=1849

Tropic Sun 5,500K Fluorescent Lamp (I think this K is too low):
http://www.bigalsonline.com/catalog/product.xml?product_id=23759;category_id=1849

Day Max Freshwater Fluorescent Lamp:
http://www.bigalsonline.com/catalog/product.xml?product_id=23597;category_id=1849

[Captain Hook]

I know the powerglo will grow plants well but it is a very white light so you may not like that. The aqua and floraglo aren't very good. I have also heard good things about the lifeglo bulb (6700K).

That Tropic Sun bulb would also be a good choice. 5500K is the closest replication of colour to natural sunlight. It will be more yellow looking I think.

[Aquarius0015]

Unfortunately the Life-Glo does come in the 15" from Big Al's. :(

Is the white or yellow light better for plants? It does not make a huge difference to me.

[Godslayer]

The kelvin rating is just a measure of how the light will look to the human eye. It has no relevance on plant growth. As mentioned, the higher the rating the more whitish/blue/bright the bulb will look. The lower the rating, the more yellowish/dimmer it will look. Personally I like higher K ratings, usually around 8000-10000K.

My opinion... I would go with the first one. However they all should grow plants well.