Par readings not accurate?

[jordanrb]

Testing the lighting in my tank with a new par meter. The numbers vary quite drastically in the same spot. Is this due to reflections in the water flow or something else causing this issue?

I get a changing range from 250-400 on the top of my rocks where I keep my sps.

 

[VintageReefer]

Do you have surface ripples? Par readings should be taken with all flow turned ofd

 

[jordanrb]

Do you have surface ripples? Par readings should be taken with all flow turned ofd

Yes I have quite a high flow. That is 100% my mistake. I figured the readings are best done natural how the system runs regularly. I will turn off and check the readings tomorrow. Thank you

 

[painter1982]

Testing the lighting in my tank with a new par meter. The numbers vary quite drastically in the same spot. Is this due to reflections in the water flow or something else causing this issue?

I get a changing range from 250-400 on the top of my rocks where I keep my sps.

I have the same problem. I’m not sure what my corals actually receive. When someone says put it in 400 par but it bounces from 250 to 400 do you need to find an average of 400 or is the high reading of 400 what you need?

 

[jordanrb]

I have the same problem. I’m not sure what my corals actually receive. When someone says put it in 400 par but it bounces from 250 to 400 do you need to find an average of 400 or is the high reading of 400 what you need?

Apparently par readings need to be done with all flow turned off. It'll give a more stable reading and that is what you go off of.

However, I do not know if that number actually is accurate to what the coral receives as the light reflects off the ripples in the water diluting the par.

 

[Skippy The Meh]

When i measure my par i turn flow off and get consistent numbers. The fact of the mater is that water bends light. Ripples bend light in random directions. This happens in nature too. In fact more drastically than in our tanks. Just get a base reading for light setup and roll with it. This has worked thus far for me. Its my opinion that just like corals like random flow, they also like random changes in light intensity. Just keep spectrum consistent.