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PAR meter vs PAR sensor from Apogee

Discussion in 'Lighting' started by timmo11, Mar 1, 2009.

  1. JDowns

    JDowns Lifetime Charter Member
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    NP. Hopefully we can add more and more data over time.

    For me its been interesting to see the wide range of lighting, and more important just how high lighting can be. Its made me rethink how things are actually working. I think just the visualization of the data in my hands helped open my eyes to the lighting aspect of this hobby.

    I have to mention a huge thank you to the folks at AquaTouch for allowing me to come in and poke around the tanks. Great local shop with good peeps.
     
  2. SuperColey1

    SuperColey1 Guru Class Expert

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    I agree totally. Being pedantic you could say that plants currently called 'high light' plants like HC and Glosso are in fact low light because they never see highlight. lol

    They do grow in the low light area however while I concede that highlight is needed to provide low light at their level I suspect though that it is getting the CO2 to the substrate level that is the important thing to them. After all I've never seen HC or Glosso grown in highlight non CO2 tanks. Therefore the question would be (another topic really) how much light they need if indeed any more than the traditional 'low light' plants like Anubias/Ferns when high CO2 is supplied!!!

    With the bulbs I suspect that they will probably lose the 5% suggested in their first few weeks of use while they 'burn in' and then stay pretty constant for a long long time. much longer than 6 months/1 year unless used on the old electric/magnetic ballasts.

    Keep the info coming ;)

    AC
     
  3. Tom Barr

    Tom Barr Founder
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    Such insights are really the ground breakers.
    Rethinking the assumptions you had is good.

    This is more meaningful than some minor tweak and claims that it solved algae or plant growth issue ( questionable effects at best, and only small possible effects), this is huge.

    It's much like adding PO4, or realizing non limiting nutrients for plants does not = algae. Test are great, if you use them to answer the larger questions.
    Also, if you start with a general model of how plants grow, light is where it all starts and then you can reduce work/labor, increase efficacy of the resources put into the aquarium to eliminate waste, use "just enough" for light, CO2, and.......nutrients.

    As was the case with PMDD, they chose one nutrient to limit,then make sure that the others are non limiting. Here, we apply this this same concept of Liebig's law, but we now expand it and include light, CO2....and nutrients.

    We can limit nutrients to reduce rates of growth, but waste a lot of light(which is the largest $ factor in the operation over time) and increase algae risk and stunting and increased demand for CO2. If we reduce light, this reduces the risk of algae and reduces the demand for CO2 and every nutrient.
    So this makes for a much better choice if this is a goal.

    The "evenness spread" I think is also key and much more natural to what plants are typically exposed to. The real hot spots will demand much more, the weak spots much less, this can occur on the same plant!

    If things are more even, then you get more even growth and less localized issues.
    Some ask why some plants do poorly, while others are growing well, the answer might be due to this lack of evenness.

    Add CO2 localization issues, current etc, now we can see a much larger picture.
    Then you tie CO2 and light together.

    Nutrients are fairly easy by comparison, they are even throughout and do not change much, we add enough (water column + sediment either or or both)and that's it.

    Then you tie all 3 together.
    Now you have a full model to work with.

    Regards,
    Tom Barr
     
  4. Tom Barr

    Tom Barr Founder
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    There is already an answer to your question posted by Ole and Claus etc from Tropica.

    When we add CO2, the light efficiency use is increased, so we can grow plants at lower light using CO2, than we can with non CO2 methods (***the reverse it what many assume***).

    Why? Simple. The plants need less resources for acquiring CO2 since there's plenty available, so they can focus more on gathering minimal light. When there's little CO2, they need more Rubisco to fix CO2 and scavenge any tiny amount of CO2 gas. so that's less resources available for light capture.

    Tropica

    Click on "Aquaristic", then "The Biology of water plants", there's A SIMPLE STUDY on CO2 and light. There's also a good article on light right in the main section, "Light: the Driving Force" etc.

    Basic stuff, all there available from a group of aquatic plant folks and growers that operate the largest aquatic plant horticulture grow out area in Europe.

    Might help you support what you are/will be saying elsewhere to more skeptical folks.

    Regards,
    Tom Barr
     
  5. SuperColey1

    SuperColey1 Guru Class Expert

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    cheers Tom.

    From that the 'high light myth' has now been banished in my eyes. ;) Unless of course, its a non CO2 tank :D

    AC
     
  6. VaughnH

    VaughnH Lifetime Charter Member
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    So much data, so little time!

    Here is the T5HO data plotted on a log-log graph, which makes seeing the relationships between the variables easier. The two lines with different slopes are the inverse square relationship and the direct proportionality relationship, between distance and PAR.
    [​IMG]

    It looks very much like the inverse square relationship holds when the T5 bulbs are relatively close together compared to the distance to the sensor, but not when the distance is reduced too much.

    I was curious to see if the different length bulbs and different manufacturers would have a different efficiency. To do that I "normalized" the data to get PAR at the same distance for each fixture. From that I got a surprise: the Ice Cap fixture gives twice the efficiency as the others - at a given distance and wattage the Ice Cap fixture gave twice the PAR of the others, which were all about the same. I didn't expect that, and I expected the Tek fixture to be the best, just by reputation. Also, the Archaea fixture, which uses a "hammered" reflector finish instead of a mirror finish, and was the shortest of the fixtures, had about the same efficiency as the Tek and Catalina fixtures.

    More to follow.
     
  7. Philosophos

    Philosophos Lifetime Charter Member
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    Wow, nice info there. Also more evidence that these new T5HO's are completely over watted for most aquariums. You really should compile all your PAR data in to one place; I've found it to be extremely helpful.

    -Philosophos
     
  8. Tom Barr

    Tom Barr Founder
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    Counter intuitive don't you think?
    More light is required for non CO2 methods?

    But this has some limits, a little bit more light to make up for the loss in energy, but more light nonetheless at a lower end of the scale, at the higher end, this does not work since plants are really stressed from strong CO2 limitation.

    Still, folks with low light, should certainly invest in CO2, not more light, and adding CO2 does not imply you also need more light either, the reverse is actually true. Both are a bit ground breaking in concept, but the evidence is quite clear from myself, you folks with light meters, Tropica, and basic research on CO2 and light.

    Now folks should try and convince what I and George Booth have been trying to tell folks for decades, you are fine with 1.5-2w/gal.

    Maybe less if the light is T5, PC etc.....

    This is as myth defying and ground breaking as adding PO4, perhaps more important in many respects, as it will help any method.

    Regards,
    Tom Barr
     
  9. Tom Barr

    Tom Barr Founder
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    That icecap did very well on that graph.

    The clear winner if efficacy is your game.
    Where's that Detlef feller?

    Haha, he likes PUR and PAR, this should help focus a lot more emphasis on the efficacy of the light on a different level we can measure and compare, and perhaps get much more use/efficiency out of vs trying to compare bulbs etc.

    I use Tek on 2 of my tanks, I'm honestly thinking of going all T5, but they do not make a 6 ft hood, I'd have to use 2 36" long hoods for the 180.

    Catalina lights did pretty good. Tek did better.
    Good graph Vaughn.

    We should do this for PC lights, they are not going anywhere for awhile.
    If you need some MH, HQI's, I have those(don't use them anymore though)


    Regards,
    Tom Barr
     
  10. SuperColey1

    SuperColey1 Guru Class Expert

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    I phrased that badly. A little sarcastic maybe.

    What I mean is some plants 'can't be used' in non CO2 tanks not because they have high light demands but because they have high CO2 demand :)

    After all even DW admits there are many plants she can't grow in her NPTs even with what we would consider is pretty reasonable lighting at the 1.5 - 2WPG region.

    AC
     
  11. JDowns

    JDowns Lifetime Charter Member
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    Some additional notes to add.

    On my fixture when I use 240w the bulbs being used are 3" apart. The Icecap data should also be noted at a 4" spacing between bulbs. Spacing of the bulbs farther apart also will play a role in better effeciency in spread.

    I was surprised at the data on the Icecaps. I'll have to find out which ballast is used. The intensity of the Tek was surprising, I wouldn't have thought that much higher. Even with two bulbs. I can start to see a trend where a fixture should be raised to a minimum distance from bulbs to water surface just to even the spread of light while also decreasing intensity. Depth of tank in relation to depth of fixture is also notable. This is where the Archaea fixture did poorly in spread.

    Nice graphs Vaughn. That makes putting things in perspective much easier.

    A seperate thread in the Articles section would be nice. So we can have all the data in one spot.

    I'm really tempted to go to the box store and get a T12 and T8 4 bulb fixture and test them over the tank this weekend. Fixtures can get returned after use :p. Be interesting to see the relationship of light intensity there compared to T5's and PC's

    I'll be remeasuring the Icecaps every three months at the stores request. They are very curious at the longevity of the bulbs. Since there are 50 bulbs in use on the same type of setup on all the sales tanks. This will give them a much better replacement schedule. While also noting for us a usable guideline for longevity.
     
  12. JDowns

    JDowns Lifetime Charter Member
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    This was part of the eye opener for me. I've seen it discussed that a plants health in various parts of the tank could be due to light issues. So it was interesting to see just how varied par can be in a localized area, especially as you travel to the corners.

    If you consider a scenerio where CO2 concentration is borderline, how the variation in light intensity can have such a dramatic effect on plant health.

    This really makes observing a tank much more concise. Best investment I've made next to the pump upgrades ;)
     
  13. JDowns

    JDowns Lifetime Charter Member
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    The IceCap is a 660 ballast with IceCap T5 reflectors. I'll update my notes to show this.
     
  14. jeremyh

    jeremyh Junior Poster

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    I just got my Apogee meter, I'll do a whole suite of measurements on my 77gal (48x16x24) tank - it has a Coralife Lunar Aqualight 4x65W PC fixture over it.

    I'll be taking readings for 2x65W 6,700K; 2x65W 10,000K; and with all 4 tubes on. I probably won't be able to take readings with varying height above water, though - the light is on those spindly plastic legs.

    (Quick preliminary readings, though, show the 10,000K tubes to be significantly brighter than the 6,700K tubes - approx. 46 v 35 umol at the substrate)

    Stay tuned - it may take a few days for me to find the time to do this properly, this aquarium is at my office and things are pretty busy right now at work...

    Cheers,

    ~Jeremy
     
  15. VaughnH

    VaughnH Lifetime Charter Member
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    I'm having loads of problems trying to get on the Internet, so this is a day late:

    For some time now I have believed that the only thing that has a major effect on light intensity in an aquarium is distance from the bulb - for a given light fixture. In other words, it doesn't matter if a 24 watt T5HO light is over a 10 gallon or a 100 gallon tank, the intensity at 10 inches or 20 inches is the same. This has to be true unless the glass sides of the tank reflect a substantial amount of light to increase the intensity. And, I don't believe that they do.

    Also, I believe that T5HO bulbs, longer than some minimum length, all give the same intensity at a given distance from them. The added wattage of longer bulbs just allows those bulbs to provide that intensity over a longer length under the bulbs.

    I decided to try this great set of PAR data to see if my idea is correct. First I plotted the data this way:
    [​IMG]

    This collects the data from the 2 bulb, 4 bulb, etc. fixtures and treats them as if they were all from the same fixture. Then I used the "inverse square" line to get the intensity for 2 bulb, 4 bulb, etc. fixtures at the same distance from the bulb, and replotted that:
    [​IMG]

    As you can see, these data points all fall on a straight line, or close to it. From this I conclude that my theory is likely to be correct - T5HO bulbs give the same intensity at a given distance, whether the bulbs are short or long, as long as they are longer than some minimum length.

    The value of this is that when you have a new tank and want to figure out how much T5HO light is needed, you can determine that from known data from other different length T5HO bulbs, and just get the T5HO bulb that is the same length as the tank (or use two shorter ones end to end). This greatly simplifies the process of selecting the "right" lighting. This also shows that 4 bulbs give about twice the intensity as 2 bulbs, etc.

    Higher up in the tank, closer to the bulbs, the intensity no longer follows the inverse square relationship, so this is most useful for larger tanks, and with the bulbs in fixtures hung above the tank, not sitting right on top.

    Using this idea, one would pick T5HO fixtures either the same length as the tank, or two of them end to end equaling the tank length. Then pick a one bulb fixture, if the tank has a front to back dimension less than 12 inches or so, but pick multiple fixtures, mounted some distance apart, if the tank is deeper than that. If the tank is too high to get adequate intensity from one T5HO bulb, one would use a fixture with two bulbs, mounted close together, and multiples of that if the tank has a larger front to back dimension. If one wants to avoid having low intensity at the substrate, but very high intensity at the water surface, one mounts the fixtures high above the tank, at a distance equal to the tank height, for example, and uses multiple bulb fixtures.

    One more thought: The Ice Cap light doesn't show up as being nearly as superior when the data is presented this way. And, the relatively crude Archaea light doesn't seem nearly as good. This is more like what I would expect.
     
  16. Tom Barr

    Tom Barr Founder
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    Well, I think most everyone had thought it was even to begin with and not so varied. When you get data that suggest that there is this higher degree of variation and patterns, then it starts to make more sense how we have such differences.

    Some claimed this to be all due to nutrient differences in their tanks and tried to manage it that way. However, many others, myself particularly, never found such differences. Other tanks had them here and there, so something else besides nutrients was occurring, so CO2 and light needed some strong good re examination, not just accepting of the same old tired claims, myths and dogma.

    I just got irritated when these same folks who promote testing for N and P, wanted to cling to the old ways when it came to light and accept what had been written and try to use a poor peusdo EI style estimation, and not test.
    To top that off, then they also suggest that you and others need really high light watts.

    These clowns are as far as the ones that use to claim excess P or N = algae blooms. Perhaps even more so.

    This needs changed and supported well to help other folks not learn this garbage, not get in the habit of repeating/spreading it all over the web.
    Then we will get somewhere and folks can better focus on their goals, have less algae issues, increase efficiency, less overall and operating cost, better even plant growth, less stress to fish etc.............

    New hobbyists fall into these same folks telling others this backwards crap, then listen to the BS about nutrients.

    They miss the big 2 issues, CO2 and light ........and micromanage nutrients.
    Only when you addreass the light/CO2, can you fairly consider and look at nutrients.

    All this stuff ties together.


    Regards,
    Tom Barr
     
  17. VaughnH

    VaughnH Lifetime Charter Member
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    Expanding on my post above: I believe all tubular bulbs, which are about the same length as the aquarium, give the same PAR at a given distance from the bulb. That means a T12 bulb 48 inches long gives the same PAR as a 24 inch long T12, and the same is true for a T8 or T5 bulb.

    To convince myself of this I did a simple calculation of the intensity versus the length of a linear bulb, directly under it, which totals up the light from directly over head and the light from each increment of bulb length on that same spot. That gave me an equation:
    Intensity is proportional to the arc tangent of (the bulb length over 2x the distance from the bulb). And, barring mistakes, this gave me this curve:

    [​IMG]

    Most commonly used tanks are from 1.5 to 3 times as long as they are high. So, the intensity for a bulb the length of the tank would range from about .7 to about .9 (units are irrelevant), which for all practical purposes is the same number. It is only on non-standard tanks, the very long, but still only 20 inches or so high tanks, or the extra high tanks, like a 20H tank, which would fall outside of that range.

    To me that says I wasn't quite correct above - a T5HO bulb the same length as the tank gives the same PAR at the center at the substrate for all standard shape tanks, until the bulb length is short enough that much of the length is wasted length, where the electrodes are. And, the same is true for all other linear tube bulbs. But, for non-standard shape tanks my idea wasn't correct.

    So, if you want "low" light a T12 or T8 bulb at the top of the tank will give it. If you want "high" light a T5HO bulb at the top of the tank will give it. If the tank is "deep" - front to back - you need more than one of those bulbs, widely separated to get that light reasonably spread over the whole substrate, and not starving the upper front and back areas for light.

    Missing is the data for T12, T8, T5NO bulbs for PAR at the substrate, to verify this. And, of course, then there is the PC bulb, a dual linear, but generally short vs the tank length bulb.

    Are we having fun yet?
     
  18. Dutch

    Dutch Prolific Poster

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    Do we have an updated thread on this data, or where I can download it?

    Thanks,

    Dutch
     
  19. dutchy

    dutchy Plant Guru Team
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    You can have look at TPT, Hoppy's post in the Lighting section on PAR data for T5 and other fixtures.
     
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