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Hi everyone

My question is in regards to fluorescent bulbs. I have a 42G tall aquarium and am currently using one 15 watt T8 Power-Glo bulb that is rated at 18,0000K. It states the following

Promotes coral, invertebrate and plant growth. High intensity. Photosynthetic deep marine spectrum. Total illumination for living corals, marine algae and freshwater plants. Power-glo is a high intensity bulb that provides rigid illumination required by corals and freshwater plants. Fish colors are intensified while the deep marine spectrum stimulates growth of macro marine algae and other plants. Use power-glo in a wide range of habitats including aquariums, terrariums and vivariums.

Would increasing the K value promote better plant growth and/or allow me a better selection in plants? I'm looking at getting the following:

The Coralife 20,000 K fluorescent lamp is a high-intensity purified super daylight lamp that simulates the deeper ocean environment. Casting sparkling blue daylight rays, fish, coral, and, macroalgae thrive in the light. This is the ultimate fluorescent lamp for deep water aquariums. The coralife 20,000 kelvin rapid-start lamp is compatible with all standard and electronic ballasts.

Your opinions and recommendations would be most welcome!


*Mitch*

Nope. When dealing with spectrums like that it will make no difference. It might make a difference if you were using bulbs such as soft white and warm white which are designed for houses or offices and do not contain all spectrums of light. When comparing bulbs that are designed to have a full spectrum it makes little to no difference in plant growth. They will grow the same under powerglos, aquaglos, floraglos, ratings from 6,500k up to 12,000k and so on. If you want a broader selection of plants you need more light not different bulbs.

Hi,
In a "tall" tank it is usually better to use the higher
Kelvin rated bulbs. The reason is that as the Kelvin
rating increases the light spectrum is shifted to the
blue end and the blue end penetrates the water better.
Red is easily scattered and absorbed within the first
few inches of water while the blue end penetrates deeper
before being affected.

With a 42G tank and only 18 watts of light, that equates
to less than a half watt per gallon. I suspect that you
would be hard pressed to grow any but the lowest light
demanding plants. Using the higher Kelvin rating would
at least ensure that more of the light given off by
the bulb would reach the substrate where the plants are.

Just how tall is a 42T tank? If it is over 18 inches
then I would be tempted to try the 20,000K bulb.

Frank

-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Bulbs with high K ratings (12,000+) generally aren't for freshwater use. Plants can't really use that color of light very well, but algae can. If you put an 18,000k bulb in a FW planted tank, you'll end up with a lot more algae than you will plants... it just doesn't work...

Also, the light is really whitish/blueish, and everything looks totally washed out and colorless... looks rather dumb, imo...

If you DO want to use one, I reccomend that you use it with several other bulbs of different spectrums. For example, try a setup with 4200k, 6700k, 10,000k, and 18,000k bulbs... that would be alright in a rather deep tank, and you'd still get all of the spectrums, and you would end up with less algae

Basically, unless you know what you're doing, I would reccomend staying away from anything above 12,000k in a FW planted tank

HTH

Despite having an 18,000k rating all glo bulbs are reddish not blue and do not follow the usual "higher kelvin rating=bluer bulb". They contain a fairly balanced spectrum and grow plants just fine. Same with the 12,000k bulbs I use they are slightly green if you look directly at the bulb and they grow plants just as well as any 6,700k or 8,000k bulb I've used. So long as you aren't just using 1 spectrum like actinics or limited spectrum like warm and cool white which have little to no red or blue the plants will grow pretty much the same. In a tank of 2' or less depth the amount of red absorbed won't make enough difference to determine the type of bulbs you use.

Now if your custom building say a 500g tank with 4' or so of height we might want to consider what spectrum of light to use along with the fact you'll probably need MH since beyond 3' all but the blue light from a PC bulb will be absorbed. But as far as my 2' high 90g versus my shallow 20g long I see no difference in what spectrum reaches the bottom or in how the plants grow no matter what bulbs I used. It won't allow you to grow high light plants in medium or low light tanks. It's just not enough to really matter beyond visual preference.

Higher K ratings can influence the actual coloration of the plants... if I remember correctly, they can make them turn slightly reddish... something rather intresting that may be worth thinking about...

Thanks everyone for your replies! I would really like to increase the wattage but I think I'm stuck with what I have. It's a hexagon shaped tank and I only have room for the existing light fixture that came with. It also only allows for one bulb.

Thanks again!




*Mitch*

You could go with PC bulbs or with MH... MH would be a tid bit OVERKILL tho, but it'd work...

I vote PC

Thanks for the suggestions PoisonWaffle. It looks like I'm going to have to try and do some retro-fitting or, although more expensive, get a new lighting system if I want to increase the wattage. This will be tough because the lighting system on my aquarium matches the colour and wood grain of my stand.

It would have been too easy to find a single 18" PC bulb or MH bulb but I've checked Big Al's and my LFS and no luck.

Thanks again!


*Mitch*

Try www.hellolights.com for lights, they're one of the best places to get lights

You should be able to build a PC light into your current fixture (remove old stuff first, of course) as long as it's the same size... maybe try a retrofit kit...

Or you could always build a new canopy and put your lights in that, and then re-trim the bottom of the tank by putting thin strips of whatever kind of wood you used on your canopy over the trim on the bottom of the tank... but that'd be a bit of a PITA with a hex tank... it could be done tho...

I can get you some links on DIY canopies if you want?

HTH

I'm not nearly adept enough at trying a DYI project with a canopy so, I think I'll go the retrofit route and hopefully come up with something.

Can't thank you enough for your help. Very much appreciated


*Mitch*

No problem

Let me know what you decide to do, and how everything goes

So, I've decided against retrofitting and I'm looking at purchasing the following:

Coralife Freshwater Aqualight-20" 6700K Quad-96 Watt
This light features a 96 watt 6700K 4 tube (quad) square pin base compact flourescent lamp. Other features include: 2 cooling fans, sleek aluminum housing, highly polished reflector, acrylic lens cover and on/off switch. Intended for use on Freshwater aquariums. Dimensions: 20" x 7" x 2.5".

I'm limited to this unit because its small enough to fit on top of my aquarium. I also realize that my K value is considerably less than what I currently have, but is the increase in wattage not a better thing to have? I've checked to see if I can find a bulb to go with this system that has a higher K value but no luck. Seeing as I have such a tall tank (22 inches), I don't want it to be gloomy looking and I want to be sure that the light will reach the plants. So, in your opinion, should I stick with what I have or do I go with this new lighting fixture?

Thanks a bunch


*Mitch*

Anyone with opinions on this please?

Thanks!


*Mitch*

Nobody with suggestions or opinions on this??? I'd hate to spend $150.00 on something that won't do the job. Your input would be very much appreciated


*Mitch*

With this light you will have 2.25 WPG. This is pretty good amount of light. You will not be able to grow super high light plants but you shouldn't have any problem growing low and medium light plants.

6700K is the idea K rating for live plants. WPG in more important than the K rating. The K is something you can play around with a little bit depending on how you like the looks of your tank but the 6700K is really the best for plants.

55G Planted tank thread
19G Container Pond
[IMG]http://i4.photobucket.com/albums/y118/Wingsdlc/Ric

Hi Wingsdlc

So, you think this unit should be OK with my tall tank and I won't have to be concerned with a dark, gloomy aquarium?


*Mitch*

6700k will be a little more towards the yellow/red end of the spectrum, but it shouldn't be 'gloomy'. It will be a difference between your 18000k for sure, but I think you'll end up liking it much better, especially when your plants fare better. If you have any room on your tank, go ahead and keep the 18000k, it will balance it out a bit nicer for your.

Might be worth it for your to head to the LFS and have them put a few different K rating bulbs on a tank for you to look at.

Thanks Fallout for your reply. Unfortunately, I only have room for one unit. If my LFS wasn't a 4.50 hour drive away, I'd certainly get them to give me a comparison between K ratings. What kind of difference can I expect with the much lower K rating? Will the colours not be quite as bright?


*Mitch*

I have 130W 6700K on my 40 long and everything looks fine on my tank. It is a shallow tank though. Greens are nice and the fish look great too!

55G Planted tank thread
19G Container Pond
[IMG]http://i4.photobucket.com/albums/y118/Wingsdlc/Ric