# 8,000k vs 10,000k or one of each?



## fishnvw (Nov 12, 2009)

Title says it all. I am just planing ahead. 25 gallon tall tank 2 compact flourecent 21 inch 55 watt bulbs. I used this on my old reef so it has a reef setup for the bulbs there's a 10,000k and a combo 50/50. So since the bulbs are old I'm going to buy new ones anyway. So should I do just one or two and should I do 8,000k or 10,000k or one of each? I will probably read on the subject untill my eyes bleed. But I figured I should ask as well. Thank you.


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## Ahura-sama (Sep 5, 2008)

5k-6.7k for plant

10k if you like the light and dunt know about 8k.


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## ghengis (Jun 11, 2008)

I have two 10k's and one unknown (I think about 6500) above my tank and I seem to have reasonalbe success. From what I have read here and on various sites, I don't think it really matters, as long as you are between 5 and 10k. 2.5k is way too low and 14k is reef territory.


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## fishnvw (Nov 12, 2009)

For the same price I can get 6,500k or 6,700k. So either of these would be better then the other two? And should I run 2 lights 110 watts over a 25 tall seems a bit high but 55 watts seems a bit low. I am trying to work with just the one fixture. I guess I could run a lower watt and shorter bulb in one of the spots. They have 16 inch instead of the 21 inch that are only 36 watt. Can a ballast run a lower watt bulb or is that not ok? Sorry I feel like I'm rambling.


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## Seattle_Aquarist (Mar 7, 2008)

Hi fishnvw,

If it were me, I would start with just one bulb. Your 25 tall is about 20" tall, which isn't too bad; and if the reflector is good you should get good light penetration to the substrate. If you need a second bulb you could and it later add use it for a "noon burst" but I doubt you will need it. 

Maximum plant growth (photosynthesis) occurs at about 6700K but any bulb in the 5K to 10K will allow plants to grow. Personal taste as to the "color" of the tank enters into the decision as well as the "K" rating; 5K is more "yellow" and 10K is more "blue".

What ever you decide remember to start slow and gradually increase the photoperiod over a month or two to avoid heavy algae growth during the nitrogen cycle. Hope this helps!


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## fishnvw (Nov 12, 2009)

Thank you seattle aquarist that really spells it out nice and simple. And don't know if you saw my location, but I'm from tacoma. Nice to see there is another pnw'er on here.


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## Seattle_Aquarist (Mar 7, 2008)

Hi fishnvw,

There are a bunch of fish and plant people here in the Everett, Seattle, Tacoma, and Olympia area. If you get a chance, check out the Greater Seattle Aquarium Society (GSAS); just a bunch of crazy fish and plant people! October's meeting was a presentation on Planted Aquariums, the one last week was Freshwater Shrimp. December is our Christmas Party, and then a speaker in January, Plant Auction in February, and more speakers. You are welcome to show up as a guest for a meeting or two to see if you like it before joining!


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## fishnvw (Nov 12, 2009)

I will take a look I'm not new to the hobby been around quite a while. Just new to plants and there care. Thanks I will look into it.


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## Seattle_Aquarist (Mar 7, 2008)

Hi fishnvw,



fishnvw said:


> I'm not new to the hobby been around quite a while. Just new to plants and there care. Thanks I will look into it.


Same here, in fact I was out of the hobby for about 10 years and planted aquariums re-energized my interest. Most of our GSAS members range in age from 16 to 70+, guys as gals, and a lot of plant people. We are not a Saltwater club, although some members do keep salt and reef tanks.


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## newguy (Mar 18, 2006)

this is from my personal experience:

I had the coralife 6700k PC and everything was fine. Then i changed the bulb from a) 6700k to 10000k b) different brand, everything else remained same including wattage, all hell broke loose. Had massive algae outbreak. Unfortunately i did not get a chance to experiment further by changing it back to coralife 6700k bulb as the tank was taken down shortly after for moving.


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## Newt (Apr 1, 2004)

newguy said:


> this is from my personal experience:
> 
> I had the coralife 6700k PC and everything was fine. Then i changed the bulb from a) 6700k to 10000k b) different brand, everything else remained same including wattage, all hell broke loose. Had massive algae outbreak. Unfortunately i did not get a chance to experiment further by changing it back to coralife 6700k bulb as the tank was taken down shortly after for moving.


Algae does better with blue light than red; both of which are needed for proper/optimum plant growth. The reason may be as Diana Walstad pointed out in her book. Blue light has a photo-reduction effect on iron and causes it to drop out and become more available to algae.

The Coralife 6700K has a very large green spike which can only help red pigmented plants to a small degree. People in Europe tend to choose lighting more around 4100K and top out at 6000K. They probably wonder why Americans are using 'saltwater' bulbs on their planted tanks.

At any rate I suggest if you go with more than one bulb start with one and build up to more light and a mix of kelvins is best. Think of the kelvin as more how you want your tank to look - aesthetics wise. As long as red and blue light is in the bulbs spectral output you should be fine.


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