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Lumens and PAR

38K views 65 replies 14 participants last post by  lumpyfunk 
#1 ·
If you haven't read this article yet, I highly encourage it. It is long and requires a bit of understanding of biology and physics, but you'll learn a lot from it.

A Comparison Between Light Sources Used in Planted Aquaria

This came from a discussion I was having with one of our newer members, collapse. He was wondering what impact lumens had on choosing a lighting system for plants. My intial response was that lumens are far more important than color temperature or CRI and should be a prime consideration when choosing a bulb for your planted tank. But then I re-read this article and fell across this passage:

Based on the Photosynthesis Action Spectrum (the wavelengths that plants are more sensitive to), light bulb manufacturers came up with fluorescent "plant bulbs". They basically emit most of their light in the wavelengths that are more efficient for photosynthesis, namely the red and blue ends of the visible spectrum. As expected, these light sources look dim to the human eye and consequently have poor lumen ratings. Also, their color temperature and CRI ratings have little, if any, meaning. After all, these bulbs were not designed to be "seen" by humans.
Obviously, not all humans like the pinkish glow these bulbs emit, but our plants sure do.
The popular GE Plant & Aquarium bulb is only rated at 1900 lumens, yet offers a PUR (photosynthetic useable radiation) of 20.9. A generic 4100K "cool white" bulb has a much higher lumens rating of 3050, but only offers 20.5uE/s of PUR.
Recently I switched to OSRAM/Sylvania's Gro-Lux bulbs (sold at Lowe's) and these bulbs have an even lower lumens rating at 1200, yet offer a PUR of 27.4!! In the ODNO thread, ridns replaced his 5000K Phillips T8 bulbs with these same bulbs from Lowe's and even though the total lumens output has decreased, his plants started pearling within 10 minutes! The high-CRI Phillips bulb he was using (Philips TL950 5000K CRI (98) F32T8/TL950) had a standard lumens rating of 2000, yet only offered a PUR of 8.9 uE/s! He was effectively increasing his photosynthetic useable radiation by over three times even though the apparent brightness of the bulbs decreased.

Ok, so if you're still with me, what am I trying to say? Basically this, don't think you've increased the amount of light your plants can use just because one bulb looks brighter than another.

Have fun!
 
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#2 ·
Well there are plenty of views on this thread but no comments so far! I'm going to keep it up top for a while just to make sure everyone gets a chance to see it. There has been so much discussion about bulb selection recently, I think this is important information for us to consider.
 
#3 ·
I don't know if I can attribute this to the P&A bulbs or not but; since changing to them my tank has pearled like crazy every day. Prior to this I was getting pretty discouraged because it didn't. I have also started the PMDD from Rex so this could also be the reason. What ever the cause, I hope it continues!
:bounce: :angel: :hehe:
 
#4 ·
It is definitely possible that the Plantex triggered the pearling if you previously had a micronutrient deficiency, but the extreme difference in PAR between the high CRI Phillips TL950 bulb and the Gro-Lux bulb you switched to seemed to illustrate the point very well. To support this argument, would you be willing to switch back to the Phillips bulbs for a few days and then back to the Gro-Lux bulbs to see if pearling discontinues and resumes?
 
#5 ·
Last night I hooked up 2 commercial 2ft 2 light fixtures and put 4 of 20 watt standard glo lux bulbs in over my 26 gal bow front. I havent seen any drastic changes yet but the light was only on for maybe a hour.They really make the colors of the plants and the fish come out. I am curious to see what happens after a full 12 hours of use. Sam i notice on the packaging the bulb came in that it said the standard bulb was mainly for seeds and seedlings. Does that mean its got a higher output? What do you think that means?

Collapse
 
#6 ·
Now why didn't I think of that ??? I'll do it tomorrow while I do the weekly water change. This should be interesting!
:bounce: :angel: :hehe:
 
#7 ·
I'm not sure why they indicate for seeds and seedlings, but that is obviously in reference to terrestrial plants so I wouldn't worry about it. The standard Gro-Lux bulb is the one that was top on that list for regular fluorescent tubes. The Wide Spectrum looks a little bluer, and seems brighter, but only at the expense of some PAR.
 
#9 ·
Sorry.... I posted the results of the above bulb test under ODNO......
:bounce: :angel: :hehe:
 
#10 ·
you are right on about some flourscent bulbs looking dim to the eye but still providing a bunch og energy to plants. GE makes two plant bulbs. the popular GE P&A bulb is usually a "wide spectrum" (it says so by the label on the bulb) version one that emits more visible light, but they have another "narrow spectrum" that looks really really dim. almost like a pinkish purple black-light.

one important thing to note though: while there is not a direct correlation between light intensity and photosynthesis (if the light is intense but at the wrong part of the spectrum), the more intense the light, the better it is at penetrating the water, so while the GE wide and narrow spectrum bulbs might grow plants equally well in air, the wide spectrum will be better at penetrating to the bottom of the tank
 
#11 ·
the bulb that was talked about above is mainly for seeds and seedlings because it wont make things flower or grow fruit. you need different light for that, like high pressure sodium (which emits energy in a part of the spectrum that makes plants think it is time to grow fruit that is also really good for photosynthesis)
 
#12 ·
grow lux bulbs are good, but i have had lots of success with "Ott-lite" they are really bright for t-8s, and have a really high PAR
 
#13 ·
I have 55 watt PCs on my tank. I'm currently shopping for some High PUR bulbs in the 55watt PC configuration. Is there any PUR data out there for these 55 watt bulbs. Do they make the sylvania GRO-lux in a 55wattPC bulb and who sells them?
 
#14 ·
I haven't ever seen any PUR specs on PC bulbs, other than the Sylvania 55w Dulux bulbs that are only available in Europe. Pet Supply Liquidator has some Plant Grow bulbs that are 50/50 tubes like reefers use, but instead of half actinic / half 10,000k, it is half red / half 6700K. I'm dying to try them out, but they are only available in straight pin (not square pin Panasonic) configuration.
 
#15 ·
9325K 55 watt
These are the bulbs I'm using now in my All-Glass fixture. I like them a lot and they seem to have the wavelength peaks in the right neighborhood.
 
#17 ·
Looking at the bulb, they have a pinkish/violet hue. I really like the way they light the tank, they get rid of that yellowish cast I get with the 6400k bulbs. The yellowish tint in the water is probably from the flourish and maybe some tannins from the driftwood.
I just ran a little experiment: I usually run the 9325k in the back of the tank and the 6400k in the front. I just swapped them and put the 9325k in front and within 10 minutesthe front of the tank started pearling more. I think I just answered my own question.:hehe: Now I just gotta find a place that sells them cheaper than $29.
 
#19 ·
I love USA, They're only $129 here.
BTW I lived in Canada for 3 years in the mid 70s.:p
 
#20 ·
I was just wondering what kinds of bulbs are good for PC's as well... I looked on the site Gulf Coast mentioned ( I have a straight pin configuration....) and saw they have a "red/white" bulb, and then a plant growth bulb, which the picture basically showed a "red/white" bulb. I e-mailed them asking the difference and information on each of the bulbs and should get a reply soon.

-Tim
 
#21 ·
They also have a red/blue bulb. I hope they have some wavelength specs so we can make some educated decisions. Post your findings.:cool:
 
#23 ·
The blue part of the red/blue bulb is actinic, and it just wouldn't provide enough output in the wavelengths plants photosynthesize at. The white part of the red/white plant growth bulb is a high Kelvin white, with strong blue output, but still a visually pleasing tone. I have a feeling that bulb would be killer on a planted tank. I would order a pair today with a WH7 ballast if I had the funds!
 
#24 ·
You talk about ordering the bulbs with a balast... If my 2x55 watt strip I have has straight-pin bulbs, I could just order the bulbs, and put them in, right? I assumed with would be true, just to double check.

I forgot to put in my last post, I also have the 9325 K bulbs, but since my tank is a 55 and I don't have another 2x55 watt strip, the purplish hew is too much for me... But, I do think that they would nicely balance out in a tank with 4x55 PC, like m.Lemay's.

I also decided to try putting T-12 bulbs into my ODNO fixture (I am going to check it this weekend, since I really don't think the bulbs are actually getting over-driven 4x, some wire is probably off somewhere) and it worked! The first time I tried this, it didn't work, but now it does, who knows! The T8 appears brighter, it is uncomfortable to look at it, but the T12 you can stare into comfortably.

If in fact there is a wire off somewhere, I can't wait to see what the GE P&A bulbs look like 4x, and with their decent PUR, my plants should be liking it!

-Tim
 
#25 ·
Correct - the only reason I spoke of ordering a ballast with endcaps is because my caps are square pin and I wanted to add a second set of 55w bulbs for a total of four.

I kinda like the purplish hue, I might have to check out those 9325K bulbs. Dont' expect the P&A bulbs to look brighter, though! As much as the regular T12 bulb you used looks a bit dimmer than the T8, the P&A will appear to have even less output. And it is true that overall lumens are definitely lower, but like you said, their increased PUR should make a difference in your plant growth. I hope they respond.

If possible, try to get the Sylvania Plant & Aquarium bulbs at Lowes instead of the GE ones at Home Depot. They're slightly more efficient.
 
#26 ·
If anyone cares I just bought Philips TL850 Altos and they are 5000K and 86CRI. The bulb burns blueish/white and the tank looks very natural and not overly yellow or white. I have 4 bulbs on my tank, being 2 times ODNO each. My plants are pearling and growing. I paid $85.00 for a case of 25 T 8 bulbs. :bounce:
 
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