What's the best color temperature for planted tanks to avoid algae?

**fablau** · 02-22-2012, 05:12 AM

Hello to everyone,
I am trying to understand what's the best color temperature for my planted tank. I have been playing with my 75gl planted tank growing pretty well any kind of plants with a mixing of T-8 tubes such as:

1 tube 4000K, 2 tubes 6700K, 1 tube 18000K

for several months, but always having the following algae issue: after just a few days from the water change and glass cleaning, a typical green algae film always appears on my glass.

So, I began to think that maybe I didn't have the right combination of lights. So I tried to switch to 4 lights at 6700K. But the problem seemed to get worse (algae film appears faster after glass cleaning!). What confuses me mostly is that if you look at lights specifically designed for plants, they comes with different color temperatures! Some are around 2400K, others are around 5000K and other again around 6700K.

Well, if you could help me to better understand what's the right route to take, I would be extremely grateful. Maybe my problem is not the light, maybe something else?

I have pressurized CO2 (3-4 bubbles per second) and lights on for 8hr/day. I try to use EI with liquid fertilizers as better as I can. I have also tried to increase Co2 as Tom always suggest, but no luck (I can't notice any difference). I know that I could also try to have a black-out for 3-4 days to kill algae, but I am afraid that they could come back anyway.

Thank you in advance for any advice you may have for me!

All the best,
Fab.

**Tom Barr** · 02-22-2012, 08:49 AM

I do not think there is any special color temp that avoids or promotes algae much at all, there are some that we like to look at more than others, there are some that seem to produce more color due to reflectance, I'm not sure about absolute color, but the algae issue is unrelated to the bulb/color temps really in this case.
You might try daily water changes since it takes awhile for it to reappear.

This will help the plants a lot. They might be able to fix the system once they grow in and start doing better.
If you can remove 1 bulb, that might help also, or raise the light up 2-4".

3 day BO is fine, will not harm anything, but the algae might come back.

I would do 3 daily water changes and wipe everything down good, and clean the filter, then another water, then do the 3 day blackout and wipe the glass the 1st day or two.

This might work if you are careful.

**fablau** · 02-22-2012, 02:56 PM

Thank you so much Tom, I will try what you suggest and post results here.

What about "the best" color temperature for plants? What kind of light combination would you suggest?

Thank you again.

Fab.

**dutchy** · 02-22-2012, 03:12 PM

I'd suggest to use bulbs around 6500K. Best average between red and blue spectrum for plants and enough green for viewing, not too yellow and doesn't "wash out" reds.

Basically all bulbs between 3000 and 10000K will give good results, so your choice can be based on what you think what is optically appealing.

**fablau** · 02-22-2012, 09:44 PM

Thank you dutchy.

So, it is my understanding that plants are not that much requiring as "color temperature" as the market want you to believe. Am I correct?

Thanks a lot again.

Fab.

**fablau** · 02-22-2012, 10:16 PM

Another question is about output. Currently I have 2 lights at 6700K (40w each), 1 light at 6,500 (32w) and 1 light at 5000K (32w) for a total of 144w. Do you think that's ok for a planted 75gl tank?

Thank you very much again.

Best,
Fab.

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**dutchy** · 02-23-2012, 10:09 AM

Certain colour temps might make a difference, according to scientific research. But in real life: Can you notice the difference if you plants have grown half an inch more over let's say two weeks? I can't.

Bulbs that are best for plant growth are the worst for viewing. But the purpose of our tank is to look at it, right? So just choose what YOU think looks the best. Your plants won't mind a bit.

The amount of light you have is enough, maybe even somewhat on the high side.

**fablau** · 02-23-2012, 03:19 PM

Thank you for your reply, I completely agree with you.

So, I guess that the rule "2 watts per gallon" is always the best way to go... Am I right?

Thank you again!

Fab.

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I am here: http://maps.google.com/maps?ll=33.522163,-117.698534

**dutchy** · 02-23-2012, 06:55 PM

a very crude rule that might just be used as a starting point using T8 tubes, but PAR is the only right way to measure light. Even better, your plants will show you what they need. Just keep your eyes on them.