PAR Reading

[Prodigy]

Sorry, I was there for the meeting yesterday and what was supposed to be a pop by turned into a long wait but I couldn’t participate in the discussion. regardless I did want to ask one question.

When taking PAR readings, do you take it with still water surface or with surface movement as you would have during standard operation of tank?

the reason for the question is, refraction of light due to ripple of surface. The par reading will keep jumping up and down if your surface is not still. And if you measure par with still surface you know you me corals are not getting same PAR continuously but in waves.

so what is the right way to measure ?

[Lexinverts]

36 minutes ago, Prodigy said:

Sorry, I was there for the meeting yesterday and what was supposed to be a pop by turned into a long wait but I couldn’t participate in the discussion. regardless I did want to ask one question.

When taking PAR readings, do you take it with still water surface or with surface movement as you would have during standard operation of tank?

the reason for the question is, refraction of light due to ripple of surface. The par reading will keep jumping up and down if your surface is not still. And if you measure par with still surface you know you me corals are not getting same PAR continuously but in waves.

so what is the right way to measure ?

Hi,

Did I meet you at the meeting? Is this Raj?

I usually measure PAR with the pumps turned off. The shifting numbers due to turbulence makes it hard to see the reading on the meter.

Presumably, if PAR differs due to wave action from one second to the next, the average PAR would be fairly close to what you would measure under a still surface with the pumps off. Of course, you can try measuring it both ways and see how close you get.

Andy

 

 

[Prodigy]

1 hour ago, Lexinverts said:

Did I meet you at the meeting? Is this Raj?

Yes. You got great memory.

 

1 hour ago, Lexinverts said:

if PAR differs due to wave action from one second to the next, the average PAR would be fairly close to what you would measure under a still surface with the pumps off.

That makes sense. I assume that to be the case but at same time if wonder how corals see it. I wish I had a logging type par meter. I think my par meter can do it but I haven’t figured it out. I have the older quantum par meter.

[DaveZ]

I personally check par with everything turned on and water movement exactly as it would be in operation. In any spot I look for the peak par and lowest par number and then what the average number is. 
 

My rational is that if the peaks are set to the near “standard” for any coral, then there’s plenty of buffer room. I will then run a bit longer of a photo period. IMO it’s better to give corals a bit less intense par and longer useable photo period.