Whats wrong with my PAR?

Discussion in 'Other Reef Talk' started by Nav, Jul 13, 2014.

  1. Nav

    Nav Director of Marketing & Photography

    I just tested my tank with BAR's PAR meter and bit concerned with the readings. The Kessil A350W is sitting on a 40B (36x18x16) 8.5" above water level & sand is 22" from the light...

    The 3 readings below are:
    1. Kessil Blue-100% + White-50%
    2. Kessil Blue-100% + White-100%
    3. Kessil Blue-100% + White-100% + Dual T5
    Its top view readings (overflow back-center) & the #s in the center point of the tank is on the rock elevation 13" below light.


    Now to the readings... I see many others with 300+ reading on 350Ws, why is mine soooo low? Is it a wrong setting with the PAR meter? Or is this normal? Any recommendations?

    Here's the rockscape for reference.

  2. Nano sapiens

    Nano sapiens Guest

    Did you apply a compensation factor? Since LEDs tend to be heavy on blue (which the Apogee meter reads too low), add a correction factor of ~ 10 - 15% at 100% for both blue and white. At 15%, that'll give you ~ 190 PAR center for #2.

    Even so, at 13" directly under the light it does seem low. If you doubt the meter's settings, take it outside at noon on a clear day and you should see ~ 1600-1800 PAR (2000 PAR at noon at the equator).

    At high intensity, Kessil lighting is high in PUR, but not so high in PAR. PUR is what corals need to drive photosynthesis, but too much of this good thing can roast corals even though the PAR reading may not be very high. In the A350 graph below you can see the huge spike in the 'Blue' wavelengths, and the relatively low amount of other colors like yellow, orange and red which, were they in greater abundance, would contribute to a higher overall PAR value assuming the blue spectra intensities were to remain the same..

    Last edited: Jul 13, 2014
  3. bluprntguy

    bluprntguy Webmaster

    I see A350N being reported at +/- 250 PAR at 18" from the light. The narrow version is 31 degree lens and the wide is 70 degrees. You are going to see ALOT more light dissipation because of the wide angle, especially when you start getting further from the light. You can see the comparison on this page.


    I have no idea why Kessill doesn't provide better PAR value documentation like AI and Ecotech. However, I'm not at all surprised by your numbers. Once you bump it up 10-15% it seems reasonable to me.
  4. Nav

    Nav Director of Marketing & Photography

    Thanks for the insights @Nano sapiens & @Bluprntguy. Based on my readings, is it ok to turn the Kessil to 100% (#2 above)?
  5. Nano sapiens

    Nano sapiens Guest

    That's a loaded question since it depends on what corals you are keeping. When in doubt, start with a lower light level and slowly work up from there.
    Coral reefer likes this.
  6. eldiablosrt8

    eldiablosrt8 Sponsor

    The par readings on the edgesof the tank are probally right +/-the 10-15% but stretching one a 350w over a 36" tank is a big stretch
  7. neuro

    neuro Webmaster

    I was looking over RC and they mentioned it was closer to 20%, but they also don't mention what meter they were basing this number off of.
    The estimation should be based on the model of the meter since they use different sensors:


    I would look at the graph on the page and see if they have our model of our PAR meter there.
  8. Nav

    Nav Director of Marketing & Photography

    I currently don't have a good FTS so quickly put together a layout & list of coral. Would be great to see everyone's input on the intensity & any suggestions to move coral around for better lighting...


    @eldiablosrt8, Agreed, I'm saving up for a second Kessil :)
  9. F6553066

    F6553066 Guest

    I wouldn't worry about the PAR reading. Everything I've read they are not accurate for LED lights and even other lights. I talked to the Kessil people and they said the PAR readings for their lights do not equate to how much the Kessil is actually putting out. Like you at first I was concerned about the lights intensity, but after 2 years and 6kessils I not longer see any problems with them. Almost all my corals are growing well and have good color.
    I would say that from reading your post there are 2 things you should be aware of. 1. The actual usable light for the Kessil 350w I have told by the company is 24 inches sq. therefore on your tank you are not getting much light on the outer sides. 2. I can tell you from my own experience these lights can burn coral very quickly, so if you run at 100 percent make sure the corals are the type that need very strong light. If in doubt start on the bottom or mid range and work up.
    Nav likes this.
  10. denzil

    denzil Webmaster

    If it were me, I'd be using two Kessils for that size of tank. Just by looking at the picture, you can tell your tank isn't getting enough light (IMO) on the edges.
  11. F6553066

    F6553066 Guest

    Your right Denzil. This needs 2 Kessil's.
  12. Nav

    Nav Director of Marketing & Photography

    The pic was shot when I had my cheap LED bar, but I agree & saving up for a second Kessil.

    For now running Kessil at 100 blue and 75 white. Most of the corals seem to be healthy and opened up.
  13. F6553066

    F6553066 Guest

    Good. Keep a close eye on them for awhile, to make sure they are adjusting well. Good luck.
    Nav likes this.
  14. Tenny

    Tenny Supporting Member

    I agree, two Kessil's are needed for a 36" width. I have two 360WE's over a 40" width.

    I also felt my numbers were a tad lower than I expected. I forgot about the % for LED's though... and I thought it was only 5%... so if it's 15-20% that is a substantial increase... although still not close to what I was expecting.

    I had them running at 100% intensity for a bit but lowered them to 90% when I noticed a few of the corals starting to bleach. Even now some corals (scolys for example) are bleaching on the sand bed. I think the better test is how the corals are responding to the light.
    Nav likes this.
  15. Nav

    Nav Director of Marketing & Photography

    Here's my latest FTS

  16. sfsuphysics

    sfsuphysics Supporting Member

    One big problem is the wide angle nature of that model, you're essentially putting LEDs without optics over it (there are optics of course, but many LEDs come with spread distances around 120 degrees, that model of kessil has a spread of 140 degrees IIRC... so you really you're spreading that light over a really large area.

    Given the choice I would never go with the wide angle version unless you have a really large footprint tank (front to back dimensions as well). Since you already have it, I would put it much closer to the surface of the water.
  17. Nav

    Nav Director of Marketing & Photography

    Moving it closer to the surface will giver better PAR in the center but the edges will probably get very dark... So until I get my second Kessil I could keep it this way?
  18. F6553066

    F6553066 Guest

    I have a Kessil 360w over a 38 gal tank that is 14by 22 and the corals I have are looking good. At top is a frog spawn, acan, candycane,and pictina. Lower down are 2 more acans, and a number of chalices. At the bottom is a Duncan, and some open brains. The Kessil's are 9 in. from the water and a using. 56 watts. In my opinion your corals should do well within that footprint until you get a second Kessil.
    Nav likes this.
  19. sfsuphysics

    sfsuphysics Supporting Member

    Let the corals answer that for you, if they're looking good, and don't brown out, then no need to change things.
  20. Coral reefer

    Coral reefer President

    Nothing is wrong with your par. Corals look good. If you want to grow higher light corals add another light. For now, done chase numbers. Give it time.
    Nav likes this.

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