PAR Reading

[newfly]

I have a newbie questions. All the forum i read, you should turn off all the pump, so that you get accurate par reading. This is counter intuitive. I work in software for living, and you want to run the tool in the same environment the end user run the tool. For PAR reading, don't you want to keep the flow pump on, to measure the actual light the coral going to get? Why get the idealistic PAR reading ?

I do see ~50 drop with and without turbulence in the water. Maybe thats not significant enough.

 

[Bruce Spiegelman]

I actually do both, but I agree with you when I make a decision as to where to keep the lights set at -- I do the PAR I want with pumps on.

 

[JVU]

It’s not about higher or lower readings. It‘s about stable vs unstable readings. The surface agitation causes innumerable tiny lenses that diffract the light (aka shimmer) and makes the PAR reading jump all over the place.

The optimal is to turn off powerheads and leave your return pump on, either with the nozzles pointed so they don’t agitate the water surface, or if DC, turned to the minimum power that keeps the same water level (same depth).

Another way would be to collect time value averages of PAR so the jumping around gets averaged out, but I haven’t bothered to figure out how to do that on our PAR meters.

 

[svreef]

I just took some readings today with the meter sitting still on a frag rack and because of the surface agitation, the reading jumps from 290 to 375 PAR.

 

[Srt4eric]

Maybe I don't have enough surface agitation but anytime I measured par it was always a solid number.