Neptune PMK Gut Check

[mmasuda31]

I'm not sure if my PMK is properly set up and reflecting accurate PAR readings.

Light: Radion XR15 Pro G4 with diffuser set about 12 inches above water with a 12" deep tank.

Program: AB+ Program on 35% Intensity

Scenario 1:
Default AMS settings MAX: 5000 (Recommended)
MIN AMS set to -25 to offset a reading of 25 in the dark.
PAR readings are 74 with the sensor centered and about 6 inches down.

Scenario 2:
AMS settings MAX: 9999
MIN AMS set to -93 to offset reading of 93 in the dark. (Gave me a reading of 1 in complete darkness which I am told is what you want)
PAR reading around 174 in the same spot, which is about double with the default max settings.


What i'm confused about is even if I jack up intensity to 100% on this program i'm getting maybe 190 PAR Max (This intensity is pretty nuts as well). Neptune advised that the 74 reading is consistent with what they see on their Radion system.

How are folks getting 200-300 PAR readings with LED lights on their PMK? Is it the a spectrum thing, is my calibration off? I'm just trying for accuracy so any help would be appreciated.

 

[slief]

Some thoughts.

12” is pretty high off the waters surface.

The diffuser will reduce PAR.

The XR15 is a relatively weak fixture in terms of output.

If you have reasonably decent surface agitation, shut the flow off for a more accurate PAR reading.

Lastly, PAR is somewhat over rated and doesn’t tell the whole story. PUR is somewhat more important with quality lights. The bluer spectrum we tend to run doesn’t read very accurately with most PAR meters and instead they use some programming compensation to address that. How accurate the results are is a source of question.

That said, regardless of PAR readings, there are many spectacular reefs that thrive under the Radions as well as many of the other popular LED fixtures despite what some would consider to be low PAR readings compared to other light technology. The only time I use any of my PAR meters (Seneye and Apogee) is when acclimating tanks to new lights. Beyond that, the PAR meters never get used.

 

[mmasuda31]

Thanks Slief - My tank has a rather small footprint 24x20x12 so I was attempting to increase spread - Perhaps I need to look into the XR30.

 

[slief]

Thanks Slief - My tank has a rather small footprint 24x20x12 so I was attempting to increase spread - Perhaps I need to look into the XR30.

For a 24x20 footprint, the XR30 would have been a much better choice. The XR15 is too small in my experience in terms of spread for that footprint regardless of the depth.

 

[mmasuda31]

Makes sense - In your opinion would a second XR15Pro suffice or should I just opt for the XR30 (Non Pro)

 

[slief]

Makes sense - In your opinion would a second XR15Pro suffice or should I just opt for the XR30 (Non Pro)

Suffice? That depends on what you have in the tank and what you plan on doing down the line. At minimum, I'd suggest two of the XR15's if not 1 of the XR30's. One XR15 isn't enough unless you have the coral right under the light and out about 6-8" in either direction from center. The single cluster on the XR15 just doesn't have enough spread for a tank the width of yours.