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Discussion Starter · #1 · (Edited)
Hello TPT'rs,

I wanted to start a conversation about bulb spectrums.

Here's a few things I've learned about lighting, in hopes that it might make things easier on someone starting out.

Trying to figure out how much light I needed was the first roadblock I came to. Luckily I found this forum and some very intelligent people. Hoppy's Chart was a life saver, and honestly, I don't think my tank would be thriving without this piece of brilliance. With it, I deciphered that ~ 75umols were making it down to the substrate. From there I could figure out what plants I could grow.



I've come to believe these numbers are a bit high. The measurements I base my lighting on are from the substrate: 15-30 par = low light, 30-50 par = medium light, 50-90 par= high light, 90+ = algae farm.

Now that I knew the intensity of my lights I had to figure out which bulbs to use. Here's where Kelvin Temperature and Spectrum really took me for a ride. I read quite a bit of information about plants only using wavelengths in the red and blue parts of the spectrum, with green light being a waste. This is not true! Plants use light in the whole range of the spectrum, from 400nm-680nm. Here's what others have said:

"Dr. O. Elgersma (Philips). In 1982, Philips held a number of its own experiments to determine the effect of different lighting on the growth of aquatic plants. We used the following plants: Hottonia inflata , Limnophilia sessiflora , Ludwigia natans , Bacopa amplexicaulis , Hygrophilia polysperma , Rotala macrandra . The difference in photosynthesis at different wavelengths was less than 10%! The results of these data are applicable to all aquatic plants as they all have the same chlorophyll."

"In general, with regard to lamps for growing plants, most of them have a reddish hue, and is good for photosynthesis mostly in terrestrial plants. When aquatic plants are illuminated only by red light, the stems of plants are strongly stretched and look ugly. When there is a blue light, the stems and leaves of plants are much better. In addition, red light fades very quickly under water, and blue penetrates well into the depths. For this reason, it is considered that for photosynthesis, under water plants primarily use the blue part of the spectrum of light. " (The wavelength of light and photosynthesis in plants, ADA)

"Quantum yield - It shows how efficiently a plant uses light of a wavelength measured by evaluation of O2 production- the main product of photosynthesis indicating its intensity. Measurements of quantum yield as a function of wavelength for plants have shown that the photosynthetic efficiency of photons in the range 400-680nm is almost identical, (Taiz and Zeiger, 1991 Plant physiology) with a rapid decline after 680nm. The fact that green light is almost never used in the process of photosynthesis is not true. Quantum efficiency of green light is ~15% less than red light, and ~5% less efficient than blue light.



The quantum yield of the blue and green light is somewhat less than red, but blue and green light penetrate much deeper in water than red light. Within 1 foot of water 50% of red light intensity is lost, in 2 feet of water 70% of red light intensity is lost, and after 3ft nearly 90% is gone.



So, in my haste I decided to get 2 plant bulbs and 1 daylight bulb. My tank had an unflattering reddish hue which I put up with because I thought it was best for my plants. Secondly, I was getting very lanky stretched out growth from my plants. I know aesthetics are a personal choice, so I'm not trying to tell you what your aquarium should look like. Just trying to help. With that said, I looked up some info on how to make my aquarium look better while maintaining good growth and found this:

"It turns out that the total photosynthesis in plants under water, from all the wavelengths, are approximately the same from all parts of the spectrum of light."

"The fact that plants use the entire visible portion of the spectrum of light more or less uniformly allows for the selection of lighting based on aesthetics. Lamps with a color temperature of 6500K are better at color rendering than 5000K, because they have a better differentiation of blue shades - it comes from the fact that the 6500K color temperature is higher, and a higher color temperature means a greater proportion of blue and green spectrum. More green light will significantly improve all the subtle differences between shades of green and make the aquarium "brighter".

"Lamps with special PAR-spectrum enhanced red and blue portions leads to great distortions of color."

"Aquariums should prefer lamps with color temperature of not less than 5200K and a ratio of red / blue (R/B) ~ 0.6 with a slightly higher proportion of blue light - they will more accurately reproduce colors under water than the reddish light of ~ 0.8. (R/B) lamps. With 0.37(R/B) being too blue. In addition, as mentioned above, blue light is much better at penetrating water to a depth than red.

Here are some common bulbs:





Of those I like the following:

Here's a typical plant bulb for reference. Notice the reddish hue? Sylvania Gro Lux


Philips 950 (most economical)


Hagen Life Glo


Arcadia Freshwater


JBL Ultra Solar Natur


GE Ecolux Ultramax



I decided on using a Life Glo + Flora Sun + Ultra Sun(until I can buy the Philips 950).

Hope this was informative. If I was incorrect about something please let me know.
 

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couple thoughts. the over lay graph should be far larger, with instead of the graph lines being black they should all be different colors so you can differentiate between the bulbs on the same graph, because it just looks like a slobbering of black lines and you cant tell what is what. (not trying to be offensive here) just trying to give you some ideas so you can get a more satisfying result for yourself. and honestly overlays should only be done 2 at a time otherwise it gets far too jumbledhaving four layers of graph data that is all so close to one another makes it again hard to tell which is which. also on your overlays there is no way to tell which line is which bulb just by looking at the graph. people have to run back and forth between the original graphs and your overlay and try and work it out.

that's a lot of work you did especially in paint. good job.
 

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lol yeah the last one's still a bit rough. graphing so much similar data is a pain in the backside. thats generally why data like that is kept on separate graphs. again nice work. you must have spent a buku amount of time in paint to do that.
 

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Discussion Starter · #9 ·
So out of the Hagen bulbs, it looks like the aqua bulb puts out the most useable par? That's something I didn't know.. Those are the t8's right?
Yep, I've had those and they have a very unique color to them. I don't know how to describe it. It's almost a blueish pink color. It looks like it has a similar spectrum to the Sylvania Gro-lux just at a much higher Kelvin.

 

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Discussion Starter · #13 ·
Quick question...I have two of those 12 smd led bulbs over my fluval edge. I think they're .25 watts each smd? I haven't been able to grow anything with those, even low light plants. They basically just have enough power to keep things alive but not growing. Why is that? I know it's because they aren't putting out enough light, but what's the difference between the .25 watt smd's and 1-3 watt smd?
 

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Discussion Starter · #14 ·
^Added to above question. I know chlorophylls a, c², and peridinin have a "sweet spot" for using Photosynthetically Active Radiation between 465nm-485nm. That is pretty much where LED's have a good drop off. Would this lack of PAR "spike" be a reason for my stunted growth?
 

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Discussion Starter · #15 · (Edited)
What do you think is the best looking mix of bulbs? Arranged respectively from front to back:

Life-Glo (6700k)+ GE Aquarays (9325k) + Zoomed UltraSun (6500k)


GE Aquaray (9325k) + Zoomed UltraSun (6500k) + Zoomed FloraSun(5000k)
 

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Discussion Starter · #17 ·
I like the first set-up the best, as the greens are nice and crisp.
there is also nice contrast between plants and darker substrate
I think so too..it looks the most natural. The others have an artificial(pinkish) feel.
 

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Quick question...I have two of those 12 smd led bulbs over my fluval edge. I think they're .25 watts each smd? I haven't been able to grow anything with those, even low light plants. They basically just have enough power to keep things alive but not growing. Why is that? I know it's because they aren't putting out enough light, but what's the difference between the .25 watt smd's and 1-3 watt smd?
^Added to above question. I know chlorophylls a, c², and peridinin have a "sweet spot" for using Photosynthetically Active Radiation between 465nm-485nm. That is pretty much where LED's have a good drop off. Would this lack of PAR "spike" be a reason for my stunted growth?
I would recommend you start a fresh thread on this so that you can get more responses, but in a nutshell, here's my take on this.


*Those low output 1/4 watt LEDs are not nearly as efficient as better-brand 3-watt class LEDs (Cree, Luxeon, Bridgelux). That's part of the reason they aren't working for you.

*The low-output LEDs are also nowhere near the power (literally 12-20X less powerful, per LED) than the 3-w class. They just don't put out much light for plants. That's the other reason they aren't working for you.

Basically, they are just too dim unless you use massive numbers of them.

You mention the 460nm color spectrum (blue) but honestly most white LEDs I've graphed on a radiometer show a considerable spike in that exact region.
 
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