PAR Estimate Question

[NormanB]

I'm looking for an educated guess as to what the PAR might be based on the following.

A location at the surface has an estimated PAR of 900. What might the expected PAR be 12" directly below this location?

If other information would be helpful, I'll do the best I can to provide it.

Thanks in advance.

 

[J1a]

1. Partial reflection:

If the 900PAR is measured in air, there will be some loss when light gets partially reflected at water surface. Depending on the angle, about 5%-15%. Let's say 10% so the light in water will be 800PAR.

2. How high is the light from the surface?

If you know that, we can use the inverse square law. When distance doubles, the intensity will be quartered.

So if your light is 12" from the surface, then you are expecting maximum of 200PAR at 12" deep.

3. Scattering and absorbance.

Depends on how much particulate and dissved organics in the water, there will be further loss, sometimes significant. It's hard to estimate this portion.

4. Light blending.

Multiple lights interact and overlap. So depends on your setup, you may have higher PAR at a lower position.

 

[TheReefDiary]

I'm looking for an educated guess as to what the PAR might be based on the following.

A location at the surface has an estimated PAR of 900. What might the expected PAR be 12" directly below this location?

If other information would be helpful, I'll do the best I can to provide it.

Thanks in advance.

what phone do you have? there's an app that works well with Samsung new model phones and iPhones called photone. it's pretty accurate.

 

[NormanB]

Good information!

I have an older Samsung S8+ and using the app Luxmeter.

Thanks!

 

[NormanB]

I know this is a very crude method, but I can't justify $500 for a dedicated PAR meter.

 

[thatmanMIKEson]

I know this is a very crude method, but I can't justify $500 for a dedicated PAR meter.

I thought that to once but I've saved more than 500$ worth of coral since getting one, I feel like it's paid for itself so every time I use it now it's profit$$

I figured this was going to be in the 2-300 range max............

 

[NormanB]

I thought that to once but I've saved more than 500$ worth of coral since getting one, I feel like it's paid for itself so every time I use it now it's profit$$

I figured this was going to be in the 2-300 range max............

Which meter is that?

 

[thatmanMIKEson]

Which meter is that?

Mq-510

 

[mrpontiac80]

I thought that to once but I've saved more than 500$ worth of coral since getting one, I feel like it's paid for itself so every time I use it now it's profit$$

I figured this was going to be in the 2-300 range max............

I felt the same when I got mine. Figured I could “rent” it from brs for $100 and return it but ended up keeping it because my guess was so far off it was laughable

 

[thatmanMIKEson]

I felt the same when I got mine. Figured I could “rent” it from brs for $100 and return it but ended up keeping it because my guess was so far off it was laughable

I did kind of the same thing lol

And the 100$ feels so wrong now

 

[NormanB]

Thanks for the meter info.

 

[mrpontiac80]

Thanks for the meter info.

Seriously though, you can always pay the cost through BRS and return it for most of the cost in 60 days. They used to rent them but this is how they now do it.

 

[Scorpius]

BRS has the Apogee 510 on sale right now. I bought one myself.

 

[oreo54]

I'm looking for an educated guess as to what the PAR might be based on the following.

A location at the surface has an estimated PAR of 900. What might the expected PAR be 12" directly below this location?

If other information would be helpful, I'll do the best I can to provide it.

Thanks in advance.

Distance from light face to surface?
Inverse sq rule rarely works here. Light is not a point. Multiple overlapping points.

"IF" 900 is accurate and assuming 12" light to surface another 12" down could be around 400.
At 24" 200- ish par.
Error % can be high especially in a tank.

I was going to post someone "tank shot" with par measurements but thought this would be better.
Finnex tested in air and an older Apogee ( daylight spectrum) but in tank won't change the principal.

6" 186
12" 119
18" 73

Inv sq would predict:
6" 186
12" 46.5
18" 11.6

Linear:
6" 186
12" 93
18" 46.5

Within certain short ranges par loss is fairly linear.

Keep in mind if one actually used a marine set sensor but measured in air. Divide 900 by 1.3 for select Apogees.

 

[thatmanMIKEson]

BRS has the Apogee 510 on sale right now. I bought one myself.

Don't rub it in! Lol

 

[Lavey29]

900 par? Are you cooking bacon? Get the free photone app on your phone. I found it to be fairly accurate for non water par checks. Some people put their phone in ziploc bags and measure underwater too.

 

[J1a]

900 par? Are you cooking bacon? Get the free photone app on your phone. I found it to be fairly accurate for non water par checks. Some people put their phone in ziploc bags and measure underwater too.

900-1200 PAR, imo, is sweet spot for some acros.

 

[oreo54]

900 par? Are you cooking bacon? Get the free photone app on your phone. I found it to be fairly accurate for non water par checks. Some people put their phone in ziploc bags and measure underwater too.

It's not uncommon...though I would correct the sensor for " air" if sensor broke the surface
Mq-200 error is only like 1.14 though.745-ish. IF I remember correctly.

LED Lighting PAR Reading Advice

Good Evening I have recently been wondering why my SPS Polyp extension is poor, and I have narrowed down a lot of things down to the below. Water parameters are all as expected and within tolerance, Latest ICP had corrections for Iodine and manganese, only minor. Nitrates are at 2ppm. 1...

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[Lavey29]

900-1200 PAR, imo, is sweet spot for some acros.

I'm sure some can tolerate that level but everything else in the tank gets fried unless of course you are pursuing a certain type of high par coral only tank system or have a large deep tank.

 

[Adolfo]

I thought that to once but I've saved more than 500$ worth of coral since getting one, I feel like it's paid for itself so every time I use it now it's profit$$

I figured this was going to be in the 2-300 range max............

Same here