PAR Data-Spiral Power Saver Bulbs, lighting question

[Homer_Simpson]

Great information i4x4nMore. Thanks. It was just what I was looking for.

[milesm]

thanks Jeremy for the very informative reply. i also think it should be made a sticky.

one final request, if i may. could you provide lighting data for the three tanks. that is, how are your bulbs oriented/kind of reflector, types of bulbs, wattage, k, distance from light to bottom of tank, size of tank. i think it would be instructive to look at. thanks.

[skratikans]

wow, this truly gives a whole new meaning to a non co2 injected tank, So I have to ask, were all three tank pics non co2? Amazing..

[i4x4nMore]

Originally Posted by milesm

one final request, if i may. could you provide lighting data for the three tanks. that is, how are your bulbs oriented/kind of reflector, types of bulbs, wattage, k, distance from light to bottom of tank, size of tank. i think it would be instructive to look at. thanks.

Yes, I can do this once I'm back in town... currently traveling.

Originally Posted by skratikans

wow, this truly gives a whole new meaning to a non co2 injected tank, So I have to ask, were all three tank pics non co2? Amazing..

I was wondering when someone was going to ask that... The top and bottom tank were run as non-co2, the middle tank was co2 injected (as is evident from the drop checker hanging on the side of the tank <wink>).

The bottom tank has a CO2 system, but I only used it in the beginning of that particular setup. I found that it was growing way too fast. I couldn't keep up with the plant trimming. So, I slowed the growth rate down... Since it has a soil substrate, I stopped the co2 and reduced the light from 120 umols/m2/s down to 60 umols/m2/s using a photographic neutral density filter on a piece of glass directly below the lights. That's another way you can control your lighting if removing a bulb is not an option or if you can't change the distance.


The reason I showed all three tanks together was that I wanted to illustrate that a non-co2 tank doesn't have to be the ubiquitous anubias/crypt/javafern style tank. I prefer brighter, sparkling tanks with verdant growth ;-)

My successes are modest, and I'm not claiming to be a master of this. But I hope to attract others with the same mind set and share our experiences and methods.


Cheers!

[epicfish]

Hey Jeremy,

Any way we could get shots of the reflectors used in your tests? ie: The one for the vertically mounted bulb and the horizontally mounted bulb.

Thanks.

[rrrrramos]

I think this is one of the most helpful posts I've read on here. I read it before lights on on my 2.5g tank, that's had somewhat of a halt on the HC growth, and the leaves were starting to get a little pale. I raised the light 1.5" before lights on and it looks nice and green like it should again!

[Hoppy]

That is some really great PAR data for power saver bulbs. I plotted the data on log log paper to see what kind of relationships are there. It looks like the light intensity drops a little faster than if it were just an inverse square drop off. I'm not at all sure why that would be. Also the relationship between intensity and bulb wattage isn't quite linear, with the intensity increasing a bit faster with power than if it were linear. That is understandable because there is more area radiating light with the higher wattage bulbs and less dark area of tube. Also, at equal distances between the light and the sensor, the vertical mounted bulb gives about 55% more intensity than the horizontal mounted bulb. That is probably from less restrike.

The data also has a lot of practical use for guesstimating how many of what wattage bulbs will give a 100 micromol (for example) intensity at the substrate for any given tank size.

Thank you very much for doing this.

[kozlany]

I really enjoyed those illustrations too. Made it easily understood to a non techy person.

[skratikans]

yeah I must of not seen that drop checker..lol..I was so focused on checking out those foreground plants...lol, will the tanks by be small...I still love the meaning behind them, it's nice to know something like that is possible

[i4x4nMore]

Originally Posted by kozlany

I really enjoyed those illustrations too. Made it easily understood to a non techy person.

Cool, I'm glad. That's what I was aiming for. Was quite fun to do. If we all talked in terms of PAR instead of watts, it would eliminate a lot of variables in diagnosing setups. I do wish the meters themselves were cheaper, I know that is the main barrier for hobbyists.

Originally Posted by Hoppy

That is some really great PAR data for power saver bulbs.

I also was a little surprised at how useful they could be.

Originally Posted by Hoppy

I plotted the data on log log paper to see what kind of relationships are there. It looks like the light intensity drops a little faster than if it were just an inverse square drop off. I'm not at all sure why that would be.

Raising or lowering the reflector over a small tank like that is going to change the light distribution and also reflect off the side glass differently. That divergence from the inverse square relationship basically indicates how the reflector shape and material comes into play. Additionally, the water itself absorbs the light in addition to the inverse square law, no?

Originally Posted by Hoppy

Also the relationship between intensity and bulb wattage isn't quite linear, with the intensity increasing a bit faster with power than if it were linear. That is understandable because there is more area radiating light with the higher wattage bulbs and less dark area of tube. Also, at equal distances between the light and the sensor, the vertical mounted bulb gives about 55% more intensity than the horizontal mounted bulb. That is probably from less restrike.

I also think that restrike is a huge factor in limiting the radiating light in the horizontal configuration. But that's what is great about using the PAR meter... if you reconfigure your lighting, you can see in realtime what the effect is going to be in terms of photosynthetic energy for the plants. That 55% increase is not very noticeable to the naked eye, yet it is there.

Originally Posted by Hoppy

The data also has a lot of practical use for guesstimating how many of what wattage bulbs will give a 100 micromol (for example) intensity at the substrate for any given tank size.

Yes, a virtual PAR meter of sorts. The thought had crossed my mind... but without accounting for reflector types, light distribution variations, water depth, turbidity, and brand of bulb, you're still back to not knowing exactly how my photosynthetic energy you really have.

Originally Posted by Hoppy

Thank you very much for doing this.

You bet.

Originally Posted by epicfish

Any way we could get shots of the reflectors used in your tests? ie: The one for the vertically mounted bulb and the horizontally mounted bulb.

Sure, however, there's not much left to the imagination concerning those two fixtures shown in the diagrams. The metal dish reflector is the exact same material on the inside. The desk lamp is simply painted white on the inside. However, I can photograph the interiors when I get back in town.

Originally Posted by rrrrramos

I think this is one of the most helpful posts I've read on here. I read it before lights on on my 2.5g tank, that's had somewhat of a halt on the HC growth, and the leaves were starting to get a little pale. I raised the light 1.5" before lights on and it looks nice and green like it should again!

I have no doubt that raising your lights caused a visual difference to you, but the real question is "what was your photosynthetic energy before you raised the fixture, and what was it after?" Such a change in the lighting would take a bit of time to see the results in terms of the growth of your plants - especially with non-co2 - probably on the order of weeks. By raising the light a couple of inches, you are effectively reducing the photosynthetic energy being supplied to the plants... that will, in turn, reduce the demand for nutrients. If there is less demand for nutrients, then your substrate may have a better chance at providing them through normal bio-chemical reactions.

By using this PAR meter, the idea here is to remove the notion of "how much light/watts do I need?" Instead, we focus on how much photosynthetic energy (PAR) is being supplied to the plants. This is not something you can determine just by looking at the setup, or knowing how many watts you have. Maybe you were overdriving the bio-chemical system in your tank, maybe not. A PAR reading would give us a better answer.

If you were already in a good range, then maybe your paling HC is because of a lack of nutrients overall. Do you see how this conversation would be a lot different if you said "I am providing X amount of photosynthetic energy to my plants, but the HC hasn't been doing well." ? Then we could immediately know if your lighting was at fault or not, and then move on to other factors.

Originally Posted by skratikans

yeah I must of not seen that drop checker..lol..I was so focused on checking out those foreground plants...lol, will the tanks by be small...I still love the meaning behind them, it's nice to know something like that is possible

Yes, I understand, totally :-)


Cheers all!

[Hoppy]

Originally Posted by i4x4nMore

Cool, I'm glad. That's what I was aiming for. Was quite fun to do. If we all talked in terms of PAR instead of watts, it would eliminate a lot of variables in diagnosing setups. I do wish the meters themselves were cheaper, I know that is the main barrier for hobbyists.

I also was a little surprised at how useful they could be.


Raising or lowering the reflector over a small tank like that is going to change the light distribution and also reflect off the side glass differently. That divergence from the inverse square relationship basically indicates how the reflector shape and material comes into play. Additionally, the water itself absorbs the light in addition to the inverse square law, no?

The water absorbs almost none of the intensity at these depths, and actually tends to focus the light due to the refraction at the surface. I suspect and my data indicates that there is very little difference in the intensity whether the water is there or not. Reflection off the front and back glass has been shown to be significant by others, but the exact contribution I'm not sure of.

I also think that restrike is a huge factor in limiting the radiating light in the horizontal configuration. But that's what is great about using the PAR meter... if you reconfigure your lighting, you can see in realtime what the effect is going to be in terms of photosynthetic energy for the plants. That 55% increase is not very noticeable to the naked eye, yet it is there.

Too bad it is so much more difficult to design a multiple bulb fixture with each bulb having a reflector like that. Intuitively I have thought it would be more efficient, but I haven't figured out how to design that.

Yes, a virtual PAR meter of sorts. The thought had crossed my mind... but without accounting for reflector types, light distribution variations, water depth, turbidity, and brand of bulb, you're still back to not knowing exactly how much photosynthetic energy you really have.

We don't really need to know the exact PAR value, just a good approximation. Even that is hard to do, with all of the variables involved.

Sure, however, there's not much left to the imagination concerning those two fixtures shown in the diagrams. The metal dish reflector is the exact same material on the inside. The desk lamp is simply painted white on the inside. However, I can photograph the interiors when I get back in town.


I have no doubt that raising your lights caused a visual difference to you, but the real question is "what was your photosynthetic energy before you raised the fixture, and what was it after?" Such a change in the lighting would take a bit of time to see the results in terms of the growth of your plants - especially with non-co2 - probably on the order of weeks. By raising the light a couple of inches, you are effectively reducing the photosynthetic energy being supplied to the plants... that will, in turn, reduce the demand for nutrients. If there is less demand for nutrients, then your substrate may have a better chance at providing them through normal bio-chemical reactions.

By using this PAR meter, the idea here is to remove the notion of "how much light/watts do I need?" Instead, we focus on how much photosynthetic energy (PAR) is being supplied to the plants. This is not something you can determine just by looking at the setup, or knowing how many watts you have. Maybe you were overdriving the bio-chemical system in your tank, maybe not. A PAR reading would give us a better answer.

If you were already in a good range, then maybe your paling HC is because of a lack of nutrients overall. Do you see how this conversation would be a lot different if you said "I am providing X amount of photosynthetic energy to my plants, but the HC hasn't been doing well." ? Then we could immediately know if your lighting was at fault or not, and then move on to other factors.

Cheers all!

[i4x4nMore]

Originally Posted by Hoppy

The water absorbs almost none of the intensity at these depths, and actually tends to focus the light due to the refraction at the surface. I suspect and my data indicates that there is very little difference in the intensity whether the water is there or not.

I respectfully disagree with this statement. By using the meter, I have measured a loss of about 20 umols/m2/s just by measuring immediately above and below the water surface. Whether this is due to a lens effect, surface reflection, or simple absorption I'll leave open for debate. But there is a significant loss due to the water. I can follow up with more precise measurements when I return from my trip.

Originally Posted by Hoppy

We don't really need to know the exact PAR value, just a good approximation.

I think even with the meter, you're only getting an approximation of PAR to start with. In the realm of quality spectrometers, the meter I use is a lower quality meter. So why approximate it further than that? If we attempt to do that, we're just back to the same problems associated with using watts-per-gallon as a metric for photosynthetic energy. Too much guessing.

Originally Posted by Hoppy

... [Good approximation of PAR] - Even that is hard to do, with all of the variables involved.

Precisely - that is the main reason for my involvement in this thread. I wanted to illustrate that you can't take someone else's setup and apply it to your situation with out accounting for all the variable factors. Or, put another way, you can't get a good approximation of PAR values unless you attempt to duplicate, in every aspect, the setup that produced those PAR values.

I originally set out to answer AirSong's original question of how much light she needed over her 2.5gal aquarium. But I worked backwards... I duplicated her setup and showed what kind of PAR she could get out of it by varying distance and bulb wattage.

Unlike most, you have an ability to correlate data mathematically to show trends; which allows you to extrapolate the data and make further assumptions so that you can apply it to a different situation. But, I suspect that most of the hobbyists here find that pretty daunting. And ultimately, it pushes them away from what PAR is and why it's better to use when discussing lighting for plants. It doesn't have to be that complicated. In my opinion, the mechanism of a simple meter reading is the only way PAR will ever be embraced by hobbyists, not through log plots and approximation functions.

The results presented in this thread will help people that want to set up something similar to AirSong's setup, using the same size tank, and the same type of light fixtures and bulbs. I just provided a few extra variations showing how easy it is to affect the photosynthetic energy provided to the plants.


Cheers!

[Hoppy]

Those of us fortunate enough to belong to a local aquatic plants group can urge that group to make a group purchase of a PAR meter for all members to use. Then we can do as you say - just measure what we have and make the changes needed to get what we want. Those who aren't that fortunate have to either spend $250 or so on a PAR meter, find someone willing to loan one, made a wild guess, or go by an approximation that gets them close. That is the only value of plotting the data and extrapolating it. Without that, we are stuck on watts per gallon.

[AquaVu]

Thanks so much 4X4. This is absolutely the best and most informative I've read on this forum. Let's make this a "sticky" right away

[Hilde]

Originally Posted by i4x4nMore

Even in my non-co2 soil tanks, I dose 10ppm nitrates and 2ppm phosphates and 0.2ppm iron each week.

I have found that you can't always just use ferts others are using, for the gh and kh of the water will determine nutrients that need to be added. I find it easiest to add ferts in the substrate. My favorite at present is natural charcoal.

I would like to know your water parameters i4x4nMore