PAR and depth relationship question.

[Delapool]

Is it possible to work out the PAR at one depth if known at another? I know I have say PAR of 50 at 1ft depth and trying to work it out at 2ft depth (and too lazy to shift meter).

Was thinking of going off charts but thought there might be a rule as well?

 

[Caliban07]

Is it possible to work out the PAR at one depth if known at another? I know I have say PAR of 50 at 1ft depth and trying to work it out at 2ft depth (and too lazy to shift meter).

Was thinking of going off charts but thought there might be a rule as well?

Delapool ? you own the one tool that most of us wish they had and that will give you the most accurate measure of PAR. Use it I say!

I do not know of any calculations. Every time I have looked in to this or something similar the answer is PAR meter every time.


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[Mr tap water]

I would imagine it would be difficult to create an accurate chart as every tank water clarity is different, so as said above just popped the sensor in and don't be lazy LOL[emoji1]


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[Delapool]

I know, I know A bit slack on my part. It's just that I'd have to set meter and then put covers and lights back on, take measurement and repeat. I guess that doesn't sound too bad for a Friday night now I think about it. Will try to do next week while tank is nice and clear of plants. I did find this below which I think I had seen before.

"Because light intensity drops approximately proportional to one divided by the distance from the light squared"

 

[Caliban07]

I know, I know A bit slack on my part. It's just that I'd have to set meter and then put covers and lights back on, take measurement and repeat. I guess that doesn't sound too bad for a Friday night now I think about it. Will try to do next week while tank is nice and clear of plants. I did find this below which I think I had seen before.

"Because light intensity drops approximately proportional to one divided by the distance from the light squared"

There is a scientific equation with respect to the inverse square law however, although the principles are there, in a fish tank there's lots of potential for discrepancies.

The par meter will tell you more.


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[Delapool]

It's a good point. And I forgot about testing corners of tank. Perhaps if I did just under lights, one foot down, at substrate 2 feet down and then each tank end at substrate?


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[Caliban07]

It's a good point. And I forgot about testing corners of tank. Perhaps if I did just under lights, one foot down, at substrate 2 feet down and then each tank end at substrate?


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You should measure all areas of the tank for comparison, then you know which areas receive more light etc. PAR will be different at each leaf on most plants even as with stems the higher leaves will receive more PAR and dense plants will be shading each other so PAR will vary all over. I would just measure each corner, back middle, front middle and across the middle. Wrote my figures down and have done with it. I don't know how much of a pain this is though or (forgive me) what this will tell you. You might also want to use the drop checker in these areas too. See I there is any difference in colour around the tank. I wouldn't worry too much. I haven't a clue what my PAR is and your tank looks great.


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[Delapool]

You should measure all areas of the tank for comparison, then you know which areas receive more light etc. PAR will be different at each leaf on most plants even as with stems the higher leaves will receive more PAR and dense plants will be shading each other so PAR will vary all over. I would just measure each corner, back middle, front middle and across the middle. Wrote my figures down and have done with it. I don't know how much of a pain this is though or (forgive me) what this will tell you. You might also want to use the drop checker in these areas too. See I there is any difference in colour around the tank. I wouldn't worry too much. I haven't a clue what my PAR is and your tank looks great.


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Thanks, I'll give this a shot and see how far I get before the novelty wears off I'm thinking that I may be able to attach the light meter to a stick so I could then move it around and get readings. Might see if I can rope one of the family members in to read the computer while I move it around (just got to think of a good bribe).

 

[Caliban07]

Haha. Tell them you won't talk about your fish tank for a whole week.


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[Delapool]

Haha. Tell them you won't talk about your fish tank for a whole week.


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That would work brilliantly (just got to get them to believe I could do it lol). I'm not sure the ph meter is the best on these Seneye's (might be accurately inaccurate) but could try recording that as well and just see if fairly uniform.

 

[Goldguru]

Par estimation tool

not sure im allowed to post links but here goes anyways.
I believe this tool was created with help from Tom Barr & others.
due to you already having a meter? so you should be able to reproduce your readings with the estimator & then apply those settings to determine what Par would be @ different depths in your tank.
Rotala Butterfly | Planted Aquarium Light Calculator

 

[Delapool]

not sure im allowed to post links but here goes anyways.
I believe this tool was created with help from Tom Barr & others.
due to you already having a meter? so you should be able to reproduce your readings with the estimator & then apply those settings to determine what Par would be @ different depths in your tank.
Rotala Butterfly | Planted Aquarium Light Calculator

Hi, many thanks for this - I didn't think about looking into these at all. Had a quick play on it to dial it into my readings and looks useable. My PAR readings still seem low which could be its a fairly cheap meter but need to dig out measurements and do properly. I couldn't get an order for the Apogee PAR meter sorted so with the Aussie dollar crashing went for the Seneye Reef meter (which is nice for the figures but a lot cheaper).

But you are all correct, I should test with the actual meter and as off sick today lifting some lights on and off doesn't sound too strenuous.

 

[Goldguru]

the math

link to how to calculate what PAR should be off to the side of Measured center.
Massaged PAR Data for T5HO lights - Aquarium Plants - Barr Report 1-44 posts

the thread which gave birth to the calculator.

Lighting an Aquarium with PAR instead of Watts - The Planted Tank Forum 1-455 posts

as you can see im well read on the subject..lol

second link is more/same as 1st I was just showing the time line on How Watts/Gal is the wrong way to think about PAR.
I believe only the 1st link contains the offset equations..
the barr report has some recent LED stuff

 

[Delapool]

Posted readings in tank thread so I can find it again. Link below:


http://www.aquariumadvice.com/forums/f19/delapools-150-gallon-tank-342669-28.html#post3375749