Confused about the way bulbs make plants look

[gotplants]

I've been reading up on the bulb combos and how everyone has their own personal preference. I have a Coralife 2x 24 watt T5HO fixture. Anyway, I had a 10,000k T5HO 24 Watt and a 6,700k Hagan Life Glo T5HO 24 watt on my tank. They are currently 15 months old but I just found out a couple days ago that my 10,000k bulb died on me.

The baby tears were doing fine and still growing great but I didn't like the color. After reading up on it, I checked my bulb and I guess the 10,000k(which went out) balances out the 6700k which gives a yellowish tint. That's why I think my baby tears looked kind of weird.

So is it the k part that gives certain colors or the type of bulb? I went to the LFS to replace my Coralife 10,000k but they didn't have one so I ended up buying an Aquatic Life 6000k bulb. When I put it in, I don't think I saw that much of a difference in the color of the baby tears.

I'm prolly going to have to replace my Life Glo pretty soon and I was wondering if I should just get that again or go for a different bulb. I bought the 6000k Aquatic Life one because the guy said it gives off a white light which I was looking for to balance the yellowish tint of the Life Glo..

[DarkCobra]

"K" is degrees Kelvin. Similar to Celsius, except it starts counting at absolute zero (the coldest possible temperature), instead of the freezing point of water.

Consider an old-fashioned incandescent bulb. When on, the filament's temperature is at 2,700-3,300K. The color it produces is distinctly yellow. The K value represents both the real temperature of the filament producing the light, and the characteristic color of the light; that's why K is called the "color temperature".

Turn down the temperature by putting it on a dimmer, and you get redder light. If you could also turn it up past 100% (without blowing the bulb), the light would get whiter, and be considered neutral white at about 6,500K. Proceed past that, and you get more blue.

Fluorescent lights don't rely on a filament being at a particular temperature to produce a particular color of light. Internally, they produce mainly ultraviolet light; then convert that to any color blend desired by a mix of phosphors coating the inside, which the UV causes to glow.

Because of this absolute freedom to produce any color blend, K cannot perfectly represent the color of a fluorescent bulb; only the average color tone. A 6,500K bulb is still some form of neutral white. A 10,000K bulb will always be bluer. But compare 6,500K bulbs from different manufacturers, and you will see subtle differences. That's why folks have specific brand preferences even for bulbs of the same color temperature, which differ according to their own tastes. For example, I like the DD Giesemann Midday/AquaFlora combo. It has a bit of excess yellow, but also has an uncanny ability to accentuate red plants/fish which I really like (all in my opinion, of course).

You're used to running at a color temperature above neutral white, because you had a 6,700K and a 10,000K bulb mixed together. The eye tends to adapt to that, and the sudden loss of your 10,000K bulb will make everything look quite yellow; even though it's really not. So I'd advise you give it a week or two, and see if it still looks so bad. If it does, then you have a personal preference to more blue, so proceed with getting another 10,000K bulb.

[talontsiawd]

Originally Posted by DarkCobra

Because of this absolute freedom to produce any color blend, K cannot perfectly represent the color of a fluorescent bulb; only the average color tone. A 6,500K bulb is still some form of neutral white. A 10,000K bulb will always be bluer. But compare 6,500K bulbs from different manufacturers, and you will see subtle differences. That's why folks have specific brand preferences even for bulbs of the same color temperature, which differ according to their own tastes. For example, I like the DD Giesemann Midday/AquaFlora combo. It has a bit of excess yellow, but also has an uncanny ability to accentuate red plants/fish which I really like (all in my opinion, of course).

This is pretty key. Even if you have a good idea what 10,000k or 6,500k is, not all bulbs are going to be the same. Some 10,000k bulbs I have had are very white, some have a lot of blue. Some 6,500k bulbs I have had are white, some are really yellow.

The numbers are not exact, lights put out a spectrum of color, not an exact color.

My advice, outside of familiarizing yourself with what color you should expect from an advertised kelvin range is to take the bulb back if you really don't like it. I have yet to have trouble. It's harder if you buy online. Some people like odd color combinations but in general, most people tend to like similar color spectrum. If you feel your eyes like the same as others, or display tanks you see, go with recommendations from the board. Eventually, you will find what kelvin ratings you like, what brands represent the spectrum well, etc.

[gotplants]

Alright, thanks for clarifying. It helped a bunch!! One more questions.. The Aquatic Life 10,000k says it's for Marine tanks. That's the part that confused me because I was looking for a 10,000k bulb. I asked the dude at the LFS and he claimed that it would burn my plants. I've had the Coralike 10,000k bulb in my tank until it died out and it never burnt my plants but I thought they were different bulbs.

So would it be safe to buy the Aquatic Life 10,000k bulb for Marine tanks?

[Wasserpest]

It won't really burn plants, but those bulbs might be weighted towards the blue spectrum, or they could be actinic bulbs, which are not as useful for freshwater plants. You want a "full spectrum bulb", avoid the "actinic blue" flavor...

[gotplants]

Yeah, I have an actinic bulb that came with my fixture but I don't use it. I just want a 10,000k bulb because I heard it balances out the yellow. I was just hesitant to get it because it said it was for Marine fish and the 6000k said it was for freshwater.

[DarkCobra]

In this case, it's labelled for marine use only because marine tanks are typically expected to look blue; whereas most folks prefer neutral whites in freshwater tanks.

Here's the spectrum of this bulb, which tells the full story more than K:



The red and blue peaks are present and what plants need to grow. Compare that to a DD Giesemann 6,000K Midday:



And you'll see it's not so different, as far as the plants are concerned. Still has essentially the same peaks at the same locations, just a different overall color balance.

[fishyjoe24]

most say 10,000k is for saltwater because it will have more blue. think about the ocean as you go down in the sea what does it do it gets bluer and bluer.

you can still use 10,000k to grow plants. when i had power compacts I used dual light 6,700k/10,000k and it worked find and grow my plants.

[Steve001]

Originally Posted by gotplants

I've been reading up on the bulb combos and how everyone has their own personal preference. I have a Coralife 2x 24 watt T5HO fixture. Anyway, I had a 10,000k T5HO 24 Watt and a 6,700k Hagan Life Glo T5HO 24 watt on my tank. They are currently 15 months old but I just found out a couple days ago that my 10,000k bulb died on me.

The baby tears were doing fine and still growing great but I didn't like the color. After reading up on it, I checked my bulb and I guess the 10,000k(which went out) balances out the 6700k which gives a yellowish tint. That's why I think my baby tears looked kind of weird.

So is it the k part that gives certain colors or the type of bulb? I went to the LFS to replace my Coralife 10,000k but they didn't have one so I ended up buying an Aquatic Life 6000k bulb. When I put it in, I don't think I saw that much of a difference in the color of the baby tears.

I'm prolly going to have to replace my Life Glo pretty soon and I was wondering if I should just get that again or go for a different bulb. I bought the 6000k Aquatic Life one because the guy said it gives off a white light which I was looking for to balance the yellowish tint of the Life Glo..

The current standard is the Color Rendering Index (CRI). A light which has a color rendering index >90 coupled with color temp of 5500-6000K will produce the most accurate colors of objects. Do some reading on the standard beyond what I've written.

[gotplants]

Alright, thanks for all the help guys.. It helped a bunch and I understand the lighting 100% better. I just wish I knew all this info before I went out to buy the first bulb haha.

[DarkCobra]

Originally Posted by Steve001

A light which has a color rendering index >90 coupled with color temp of 5500-6000K will produce the most accurate colors of objects. Do some reading on the standard beyond what I've written.

True, but I tried some 97 CRI bulbs once and was highly disappointed; even after waiting a few weeks to let my eyes adapt. The colors were accurate to the point of being plain, and nothing really stood out. Taught me that in an aquarium, it's better to have lighting that pleases you than have absolute accuracy.

They work spectacularly for photography and art, though.

[Steve001]

Originally Posted by DarkCobra

True, but I tried some 97 CRI bulbs once and was highly disappointed; even after waiting a few weeks to let my eyes adapt. The colors were accurate to the point of being plain, and nothing really stood out. Taught me that in an aquarium, it's better to have lighting that pleases you than have absolute accuracy.

They work spectacularly for photography and art, though.

At certain times of the year direct sunlight shines on my tank, all the rest of the time bright but indirect sunlight. I like light that makes things look like they should. And I know my plants are receiving at proper spectrum. I prefer that.

What was the bulb ?

[DarkCobra]

Originally Posted by Steve001

At certain times of the year direct sunlight shines on my tank, all the rest of the time bright but indirect sunlight. I like light that makes things look like they should. And I know my plants are receiving at proper spectrum. I prefer that.

I have one tank that gets sunlight for a few hours. Looks great. I haven't found any artificial lighting that truly looks like it, no matter how close they claim to emulate it.

Originally Posted by Steve001

What was the bulb?

I'm not home right now, but I'm pretty sure it's the Philips TL950.

[Steve001]

Originally Posted by DarkCobra

I have one tank that gets sunlight for a few hours. Looks great. I haven't found any artificial lighting that truly looks like it, no matter how close they claim to emulate it.



I'm not home right now, but I'm pretty sure it's the Philips TL950.

The spectrum.


My current light is a cfl by Eiko called ColorMaster Digital Imaging Lamps. It's used for videography. I did a comparison of the color shifting between direct sunlight at noon and it. There is a very barely noticeable shift towards the blue. I have the spectral distribution jpg, but I'm unable to post it because I don't know how to reduce the image size.

[DarkCobra]

Interesting. I never bothered to look up the spectrum for the TL950's. Doesn't have the photosynthetic red peak that's normally present in aquarium lighting.

I couldn't find the ColorMaster spectrum. Go ahead and post it if you like, the forum automatically reduces the display size of large images.

But no fluorescent produces anything resembling the true spectrum of sunlight, which is far smoother and continuous; with no sharp peaks at all:



The sun laughs at even our best artificial lights. Short of sulfur plasma, but that's still expensive. Maybe in another ten years.