PAR measurement, how do you take yours?

[Pete_the_Puma]

Hi all,

Simple question with a likely complicated answer:

Do you turn off all your powerheads/return pump when measuring PAR lighting in your tank?

Background: I have a 65G SPS tank and have been struggling with my LEDs (2x RADION x30W gen3, yes overkill). I finally decided to get a PAR meter (Seneye, not the fancy expensive ones, per BRS videos seem like all you really need) to make sure I was in the 200-300 PAR sweet spot for my sticks. I performed a series of measurement yesterday but my problem is the PAR value was varying wildly with what I assume was the waves/water movement at the surface from all the Gyres and waveameker doing their job.

On one hand I would like to measure PAR in the same conditions as the corals are exposed to (pumps and powerheads on, waves at the surface). On the other hand I think the measurement might be more stable if the water surface is unbroken and smooth.

Anyone have any thoughts about this?


Pete

 

[saltyfilmfolks]

measure PAR in the same conditions as the corals are exposed to

That.

Sorry for the complicated answer.;)

 

[DaltoniousMax]

I noticed on one of the BRS videos they did a series of test with a PAR meter and they decided that the surface agitation didnt make as much of a difference as they though. It's a short piece of this video toward the end but here's the link-
http://www.bulkreefsupply.com/video/view/brstv-investigates-testing-par-in-water-or-air/

I'm not sure how they might affect the seneye par meter specifically, I guess I would lean more towards testing in the real conditions IMO.

Interested to hear other thoughts on this as well, I've been considering one of those seneye setups largely because of the Par meter.

 

[Pete_the_Puma]

That.

Sorry for the complicated answer.;)

Yes but then the measurement is technically difficult because the meter displays rapidly changing values from say 150-350 with no stability.

 

[DaltoniousMax]

Bummer, I guess you'd have to kill the flow and assume that the still reading is an average of the agitated surface reading(?)

Seems to kinda defeat the purpose of system that is suppose to monitor tank conditions, not that par needs constant monitoring. I guess it would show if the lights went out.

 

[saltyfilmfolks]

Yes but then the measurement is technically difficult because the meter displays rapidly changing values from say 150-350 with no stability.

then turn off the pumps now and remeter and understand that the coral is actually getting between 150 and 350 par at times.

With The flow off, meter the par at different levels and areas rather than at purely coral specific locations. This is measuring the actual field of light as it descends and decreases in the tank.
Its also a shortcoming in the meters design as it doesnt compensate for the separation of colors from LED. Ie "shimmer" This is what your seeing as you meter with the water moving.
This is the difficulty in using an actual color temp meter on many un diffused leds(in other industrial applications). the multiple smaller focused beams of light don't have time to diffuse or mix before they hit the small sensor.