# [Wet Thumb Forum]-Spectrum Issue



## fullmetalninja (Jun 29, 2004)

For a planted tank, that will have community fish- should I go with two compact 6500K bulbs, or would a 10,000K/6500k Combo still give adequate plant growth, and give a better visual appearance to the tank?

Thanks for all the help(hopefully I'll be able to contribute one day).

-fullmetalninja


----------



## fullmetalninja (Jun 29, 2004)

For a planted tank, that will have community fish- should I go with two compact 6500K bulbs, or would a 10,000K/6500k Combo still give adequate plant growth, and give a better visual appearance to the tank?

Thanks for all the help(hopefully I'll be able to contribute one day).

-fullmetalninja


----------



## gpodio (Feb 4, 2004)

Two different lamps will nearly always give a more complete spectra than two of the same. Both 6700K and 10000K full spectrum bulbs will grow plants, the rest is up to your own preference. I prefer warmer tones as they do a better job of showing red plants, but most people prefer greens which are better represented by higher kelvin bulbs.

Hope that helps
Giancarlo Podio


----------



## Roger Miller (Jun 19, 2004)

I'm getting pretty tired of fighting this battle, so I'm only going to say this once.

If you want a light that gives you "a better visual apearance to the tank" then you need to use a light that is *made* to give a better visual appearance. That means a light with a color rendition index (CRI) rating over 90 -- the higher the better. You don't need to mix-and-match lamps to get a good effect.

Any high-CRI lamp will grow plants, but they tend to be more expensive than some lamps and inefficient compared to other lamps. But then, you weren't asking for cheap and efficient.

You can't tell *anything* from the Kelvin rating about whether or not a lamp will be suitable for growing plants or for viewing plants. In some cases the Kelvin rating doesn't even tell you very much about the color of the light.


Roger Miller


----------



## fullmetalninja (Jun 29, 2004)

Thanks for the help...

I've never tried to grow anything more difficult than Swords or Java Fern- so I never really paid to attention to Color ratings, etc..

So thanks for the help.

-fullmetalninja


----------



## nino (Oct 2, 2004)

Roger, 
I have a question for you. I've never read the CRI value on any of the bulbs I use and threw all the boxes out already. Do 2 bulbs with the same CRI value have exactly the same color (to our eyes)? Or one may have slight more yellow or green depending on the brands?


----------



## Roger Miller (Jun 19, 2004)

Ninob,

CRI doesn't have anything to do with the color of the light. Bulbs with low CRI ratings (70, for instance) can have a wide range of colors. Ideally you should never perceive the light itself as being colored. Lights that render colors accurately (high CRI lights) show true colors without adding shading of their own.

Think of lights as being like stereo speakers. Sound from good speakers is "transparent" -- as if the speakers were just a portal that let the music into the room. You should never hear the speakers themselves. If you do then the speakers are emitting noise and distortion.

Lights should be the same way. They should be invisible to the viewer, who perceives only the warmth and color of the objects that are lit. Any shading added by the light itself is equivalent to noise and distortion.


Roger Miller


----------



## 2la (Feb 3, 2003)

> quote:
> 
> Originally posted by Roger Miller:
> I'm getting pretty tired of fighting this battle, so I'm only going to say this once.
> ...


Though I'm steadfast in my agreement with the remainder of this post, I disagree to a significant extent with the above statement. "Better visual appearance" is itself a subjective statement, so attaching a number to it such as CRI isn't going to help unless the purchaser actually _knows_ what s/he perceives to be "better": more like sunlight, or not necessarily more like sunlight. Having seen my tanks under direct sunlight filtering in through big bay windows, I can confidently say that sunlight does _not_ necessarily bring out the "best" color in plants or fauna--only the _truest_. My preferred 67-CRI bulbs do a much, much better job of enhancing reds and blues than sunlight, and not too shabby of a job on greens, as well.

Those in pursuit of high-CRI ratings are searching for a _more accurate_ color rendition, but that does not necessarily correlate with a "better visual appearance". That lies in the eye of the beholder.

2la


----------



## Ben C (Apr 16, 2006)

actually.. "better visual appearance" lies in the eye of the _beer_holder!!

We've all been there!


----------



## gpodio (Feb 4, 2004)

Roger, I guess it depends on your preference, being a mere estetic principle, we can not assume that everyone likes the way their tank looks with 90 CRI bulbs. Some people for example like the look of the GE Aquarays which are quite low in CRI...

What I said about mixing bulbs was related to their spectrum. Unless you know you have an ideal spectrum emitted by a bulb, using different bulbs usually gives you a broader, more complete spectrum as they all differ slightly, even similar bulbs do. Mixing bulbs is a simple way to minimize any shortcomings that a single bulb may have in regards to it's spectral output. But it's not a big deal really, most of the popular bulbs we all use do a fine job on their own.

So don't take it like a battle, it's just personal preference. Look at reef tanks, some people love the way their tank looks with only actinics and their CRI is useless, I don't like it personally, 14000K so far is my preference in reef tanks, and again it's CRI isn't very good at all regardless of the bulb you choose. I also like the GE Aquarays on their own in some tanks, in particular where there are red plants. I will usually use a 6700K in front where I have glosso or similar green foreground plants as this gives a much nicer "green" than the yellowish tint the Aquarays generate. My overall CRI? I wouldn't have a clue, probably terrible , I just judge it by the way it looks. Like my music, I like a lot of highs and lows and very little mids, not your most accurate reproduction but it's how I like to hear it.

There is also the topic of different bulbs effecting plant growth and/or color. I've seen this myself as I have different bulbs on one half of the tank than the other, the same plants color up quite differently depending on which side of the tank they are grown, and that is even when comparing them under the same light.

Besides all that, I agree with your statement, if you want the most accurate representation of colors, then you want a bulb with the highest possible CRI. Spectrum is another topic and is more important for plant growth than CRI or Kelvin. Stray from a high CRI and you are enhancing, reducing or simply changing the way things look overall, it's not an accurate representation of the true color of your plants but that's not to say it doesn't agree with your own personal tastes.

Giancarlo Podio


----------



## fullmetalninja (Jun 29, 2004)

Thanks for all the input, guys/gals...

This is what happens as a newbie to the planted aquarium- you mix terms that you truely don't know what they are...

Oh well. This discussion has helped me understand some of the practical differences anyway.

Just wait until I try to hookup pressurized CO2 for the first time... The likelihood of that going well is not so good







.

-fullmetalninja


----------

