Of Plants, Light, and Colour Spectrum.....

Walker_

Walker_

AC Members
Feb 10, 2005
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Left Coast, Canada
Hi all,
I am just planning my new 90Gal tank. It will be a fresh water that is HEAVILY planted. I am wanting to make the plants the most defining feature of this tank, fish will be an after thought.
I was planning to go with 2x400W Metal Halide lamps, my question is as follows, what would be the best color bulbs to buy?!?!!?
I have seen metal hailed bulbs from between 5000K, 10000K and 20000K. What spectrum do fresh plants like the most, and what would look the best? any suggestions?
-walker
 
Plants like anything from 3500 - 10000 K in general, the lower the K number, the more yellow the light will look (fish and other stuff tend to look jaundiced in this kind of lighting)

However, too much 10000K will make the fish looked washed out as well.

I'd recommend a mix of 5000 and 1000 K bulbs, if you can do this, though you're only using 2 bulbs..

I'd go with the 2 10000K and see how you like the looks of it. I'd most definitely stay away from the 20000K
 
I would think 5000K natural daylight (high CRI) metal halides would be your best option. Personally 800W over a 90g sounds like overkill for FW. You could also do 1X400W MH and then add some NO/VHO/PC/whatever fluorescents which would give you more light qualities to choose from, and you'd still have 5+ w/g.
 
Are you going to be supplementing CO2 at that level of lighting? You would almost certainly have to at close to ten wpg. My recommendation would be anything between 6500k and 10,000k on the spectrum.
 
Yes, I was planning to have Co2 on an automatic PH trigger..... I am also planning to run a UV sterilizer to prevent major algae blooms. as well as running my Diatom filter a few times a day.....

Is there a possibility I will damage my plants with this much light? I was under the impression that for well planted tanks 10wpg is a good number to shoot for... As I was going to run one or two tubes of Florescents as well to get the numbers right up to 10.....
 
If I were to make a guess at it I would say that 4 to 5 wpg is about the max that you would want. Tanks under 20 gallons and tanks over about 75 gallons don't fall under the standard wpg rule, they actually need more. But 10 wpg I think would be overkill. High levels of light do tend to make some plants, especially stem plants, leggy.
 
Wow, yeah I would probably agree with Karnaaj on the wpg limits. Ten wpg is a whole LOT of light! I dare say you could tackle some of the most picky hard corals and anemones in a reef tank with light of that quality and amount. You must be terribly excited about setting up this tank since you obviously are willing to invest some considerable time/money.

May I suggest joining the APD (Aquatic Plant Digest) and asking some of the regulars on there what their recommendations would be for such a large display. Try http://fins.actwin.com/aquatic-plants/. Also if you havent looked at it yet, http://www.thekrib.com is another good resource for old posts from the APD about lots of different topics in planted aquaria. Last, the Aquatic Gardener's Assoc. website may be a good stopover for you, http://www.aquatic-gardeners.org/. The Aquascaping contest in particular is a great source of inspiration. Good luck with the tank.. the planning and research stages are always my favorite phase. :)
>Sarah
 
Walker_ said:
Yes, I was planning to have Co2 on an automatic PH trigger..... I am also planning to run a UV sterilizer to prevent major algae blooms. as well as running my Diatom filter a few times a day.....

Is there a possibility I will damage my plants with this much light? I was under the impression that for well planted tanks 10wpg is a good number to shoot for... As I was going to run one or two tubes of Florescents as well to get the numbers right up to 10.....
Click to expand...

I think that is nuts! IMO, anything much over 2 wpg makes you a slave to your tank.

Anything in the 3's means that you are dosing fertilizers more than weekly with water changes. Um, if it's Tuesday then I must add traces?? Wednesday is nitrates and phosphates?

Bah, I have stem plants that are growing an inch a day with 3.4 wpg only for 5 hours mid-day and 1.8 wpg the rest of the 12 hours and it is more than enough work.

Be careful what you wish for. Running a diatom several times a day... Geez.

This sounds like someone saying, "I'm going to run down the center lane of the freeway for a while, don't worry about trucks hitting me, I can run really fast if I have to."
 
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