# T5HO Bulbs: Which Kelvin Is Better?



## lonedove55 (Jan 25, 2012)

I decided to go back in my tank log and compare bulbs I was using on 26g tank for approx. 1 year. I've been using Excel (somewhat sporadically on a daily basis, the bulk of it right after water changes) and DIY CO2 (since March 8, 2013). Light is approx 19 1/2" from top of substrate. 
WARNING: Pic heavy!!
This is a picture of tank in July 2012: (1) ZooMed Ocean Sun 10,000K (1) Coralife 10,000K bulbs added 6/30/2012:










This is pic 10/15/2012: Check out the explosion of growth, especially in the wisteria! I was having to trim it nearly every week or at least every 2 weeks, with handfuls of clippings:









March 16, 2013 I changed out the 10,000K Coralife to a 6700K Zoo Med Ultra Sun bulb, reasoning being it would help with some of the diatom/algae I was experiencing. Below is a growth time line:
3/19/2013









5/10/2013:









And today 6/23/2013:









As you can see, there is very little growth in 3 months and I have not trimmed the plants hardly at all, mostly to remove leaves with quite a bit of diatom algae. Honestly? Yes, I was getting diatom algae with the nice growth (October), but I'm still getting the diatoms...sometimes I think it's worse now since changing back to a 6700K bulb. If anyone can help explain this, I would be extremely appreciative!!

P.S. DIY CO2 was removed couple of weeks ago..didn't seem to be helping much IMO.


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## Nave (May 28, 2013)

From what I understand diatoms thrive in a low light condition. Really nice set up you have there I like the time line you did it really shows what light is superior.


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## dalfed (Apr 8, 2012)

You have to remember that light bulbs are like everything else, different makers different quality! Even the k ratings can be mislabelled when doing new installs it is common to find 1 or 2 bulbs per box that do not emit the same color as the rest.
The sun is measured at 5900k that is why most people say to use 6700k bulbs (closest match) but if your water in the aquarium is slightly hued a 10000k bulb may bring the needed colors to the plant (because of refraction) better then the 6700k.
I have noticed that most of the plant nurseries run combinations of lights on there plants for best results.


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## Reefing Madness (Aug 12, 2011)

Nave said:


> From what I understand diatoms thrive in a low light condition. Really nice set up you have there I like the time line you did it really shows what light is superior.


Incorrect. Diatoms will show up when you switch lighting from low intensity to high, or change out very old lamps to new.


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## Reefing Madness (Aug 12, 2011)

http://www.aquariumforum.com/f15/aquarium-lighting-16326.html


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## Reefing Madness (Aug 12, 2011)

Blue light or more Blue light penetrates water better at depth. More so than your 65-67k lighting does. The more red in spectrum the less light getting to where its needed, the reds scatter once they enter the water surface.


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## lonedove55 (Jan 25, 2012)

Nave said:


> From what I understand diatoms thrive in a low light condition. Really nice set up you have there I like the time line you did it really shows what light is superior.


Thanks Nave. I DO know too high of lighting causes algae problems..that and an unbalance of nutrients also. 




> You have to remember that light bulbs are like everything else, different makers different quality! Even the k ratings can be mislabelled when doing new installs it is common to find 1 or 2 bulbs per box that do not emit the same color as the rest.
> The sun is measured at 5900k that is why most people say to use 6700k bulbs (closest match) but if your water in the aquarium is slightly hued a 10000k bulb may bring the needed colors to the plant (because of refraction) better then the 6700k.
> I have noticed that most of the plant nurseries run combinations of lights on there plants for best results.


 Dalfed, that's basically why I went with the 10,000K bulbs to begin with (1 bulb is a Coralife, the other is a Zoo Med, both 10K). The tank is fairly deep, plus I use a glass top which cuts down on some of the light anyway. I've found that the Zoo Med bulbs (German made) *are* slightly brighter than the Coralife brand bulbs (cheaper too!). A tank with fish only it probably wouldn't matter much, just whatever you thinks looks the best. But with plants, that's a whole different ballgame. The Zoo Med bulb has a little more of the blue spectrum than what I like, but it does seem to do a good job. They are supposed to be good for 10,000 hours, at least that's what the manufacturer claims.


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## lonedove55 (Jan 25, 2012)

Reefing Madness said:


> http://www.aquariumforum.com/f15/aquarium-lighting-16326.html













Yep, read that thread of Susan's. It's a really good breakdown on lighting,especially the above chart showing the spectrum range useful to plants. (But still somewhat confusing to my old brain. LOL)



> Blue light or more Blue light penetrates water better at depth. More so than your 65-67k lighting does. The more red in spectrum the less light getting to where its needed, the reds scatter once they enter the water surface.


Exactly what I was *trying *to achieve, more light deeper into the tank for plants closer to the substrate. Just need to tweak it enough to avoid algae problems they claim the higher blue spectrum might cause. I did leave out one critical thing though in previous post....lights during that time frame were approx. 8 hrs per day up until March. Since March, I cut the hrs back to 6 per day as the algae seemed to be getting worse (doesn't seem to be making much difference though).

I'm changing out the 6700K bulb today and putting the 10,000K back in. Planning to monitor that tank closely for any worse algae and growth rate of plants. Thanks for the replies guys!


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## Nave (May 28, 2013)

Reefing Madness said:


> Incorrect. Diatoms will show up when you switch lighting from low intensity to high, or change out very old lamps to new.


Thank you for clearing this up for me. I was told that diatoms do better in a low light condition and if you brighten the light that it can reduce this from happening. I thought this to be true cause I had a bloom I put a brighter light on the tank they went away slowly. This may have been from being a new tank.


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## susankat (Nov 15, 2008)

Paula if your going to run 10K lights you will need to dose heavily on the ferts and run co2 in order to help with the algae.

Diatoms has many causes and the main reason new tanks get it is because of the silicates in the water, substrates and such, and will go away once the diatoms use up all the silicates.


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## jrman83 (Jul 9, 2010)

My opinion is as long as you stay within the plant growing area (5500-10,000k), it all comes down to personal pref from there. You can go to any planted web site out there and nobody will tell you that you will have better grow rates with this kelvin over that kelvin and if they did they couldn't prove it. Kelvin differences should make no difference in how you take care of the tank either unless you are increasing wattage.

So really, it just comes down to you and what you like.


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