# 10k vs. 18k



## klug7214 (Dec 6, 2009)

Im adding another light fixture to my planted tank. I currently have a 10k t8bulb and I am wondering if it would be best to add another 10k or an 18k. Also when I was looking at 18k bulbs different types have different lumens. What range of lumens should I be looking for?


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## squirrelcrusher (Sep 23, 2009)

I think that 10k is the high end of the lighting spectum that you want. 18k seems to bright. I use 6.5k and 10k bulbs


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## NursePlaty (Feb 5, 2010)

*Both of the lights give off the same about of light and isnt brighter than the other. The only difference is the color. The 10,000k gives off a closer color spectrum that plants require to grow than the 18000k. 18,000k is more blueish color and might do better in a saltwater aquarium. Plants reuire a spectrum of 6700k to grow best so I would be going for the 10,000k than the 18,000k. *


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## klug7214 (Dec 6, 2009)

I saw an 18k in a tank and it is more of a purple color... It really brought out the reds in the plants and fish, it really made the tank look nice.


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## NursePlaty (Feb 5, 2010)

klug7214 said:


> I saw an 18k in a tank and it is more of a purple color... It really brought out the reds in the plants and fish, it really made the tank look nice.


*Yes it does look more nice. Actinic bulbs and 20,000k also look nice in freswater but both will do nothing to help grow live plants in freshwater. Unless you are not keeping live plants, then the 18k and actinic will be ok. 18k is just the wrong spectrum for plants. maybe 5-10% of the light will help grow. Stick with 6000k-7000k for best results. *


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## archer772 (Nov 8, 2008)

Lumens measure the light that the human eye sees so what you should be looking at is the par ratings and at what NM wave lengths are the highest.


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## James0816 (Jun 19, 2009)

10k is upper limit for planted tanks. Not too many plants can fully utilize the light on this scale. 18k will do nothing for a freshwater tank. If it is between those two...chose the 10k.

However, for best results in the planted world, look at daylight bulbs at the 6500-6700 range.


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## archer772 (Nov 8, 2008)

I feel it depends on what plants you are trying to grow to a point. I am running 1 Giesmann Aquablue PLus 11k, 1 ATI Aquablue Special 12k, 1 ATI Blue PLus and 1 GE Starcoat 6.5k on a 4 foot 120 gallon and feel that I am getting good growth but I dont have any high light plants as of rite now. I am trimming my hornwort and anacharis weekly and my Combomba and Ludwigia have doubled in size in the 3 weeks that they have been in there so I guess I am just saying that higher K bulbs can give good growth on some plants oh and NO CO2 just excel.


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