How do I figure out my PAR?
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Old 02-23-2015, 09:47 PM   #1
ChalupaBatman
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How do I figure out my PAR?


My tank is a 125g (60"L x 24"W x 24"D) and my substrate is about 3" deep. I have a 48" Buildmyled Dutch Planted 6300k (64w) sitting directly on the tank with a 90 degree beam angle. I also have a 48" Current satellite freshwater LED (18w) which sits directly on top of the tank. How on earth can I determine what my PAR is at the substrate and in the middle of the tank? Would this be considered high/med/low light?

Last edited by ChalupaBatman; 02-23-2015 at 10:56 PM.. Reason: I can't spell
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Old 02-24-2015, 03:38 PM   #2
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BML's website will tell you that a 90-degree Dutch Planted 6300k fixture at 24" deep gets you 60 PAR, or high light, directly under the middle of the fixture.

The current USA website will tell you that at 24" deep the freshwater LED gets 8 PAR.

Depending on how you place the lights, and their light spread overlaps, you can add the numbers up (assuming 100% overlap), or take off a bit for less than perfect overlap.. Your peak par is probably going to be somewhere between 68 and 64... which is still high light, but not a whole lot more than the BML gets by itself. Either way your brightest spot is still going to be right under the middle of the BML fixture.

Since your fixtures are 48" on a 60" tank, the edges will be somewhat lower light...
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Old 02-24-2015, 05:10 PM   #3
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Quote:
Originally Posted by mattinmd View Post
Since your fixtures are 48" on a 60" tank, the edges will be somewhat lower light...
And the plants there will lean in because of it.
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Old 02-24-2015, 06:47 PM   #4
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Quote:
Originally Posted by mattinmd View Post
BML's website will tell you that a 90-degree Dutch Planted 6300k fixture at 24" deep gets you 60 PAR, or high light, directly under the middle of the fixture.

The current USA website will tell you that at 24" deep the freshwater LED gets 8 PAR.

Depending on how you place the lights, and their light spread overlaps, you can add the numbers up (assuming 100% overlap), or take off a bit for less than perfect overlap.. Your peak par is probably going to be somewhere between 68 and 64... which is still high light, but not a whole lot more than the BML gets by itself. Either way your brightest spot is still going to be right under the middle of the BML fixture.

Since your fixtures are 48" on a 60" tank, the edges will be somewhat lower light...

Perfect! Thank you so much for clarifying. I feel like an idiot though since you found it all on the mfg. websites. I'll just get some low light plants for those edges.

Now the question is, should I upgrade that Current USA light to a second BML to get more even PAR levels throughout the tank or do I even need a light in addition to the BML?
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Old 02-24-2015, 07:54 PM   #5
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With the Current and the BML you will need injected CO2 to keep from
getting algae. With a lot of fast growing plants you may avoid it.
Here's the catch 22 of it...
The only reason to get the other BML would be to get brighter reds on your red plants.
But it likely won't do that without the injected CO2.
The extra BML will cost about $379 and then the CO2...
The Current seems a better choice to me because even/w that you may need the CO2.
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Old 02-24-2015, 08:39 PM   #6
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Quote:
Originally Posted by Raymond S. View Post
With the Current and the BML you will need injected CO2 to keep from
getting algae. With a lot of fast growing plants you may avoid it.
Here's the catch 22 of it...
The only reason to get the other BML would be to get brighter reds on your red plants.
But it likely won't do that without the injected CO2.
The extra BML will cost about $379 and then the CO2...
The Current seems a better choice to me because even/w that you may need the CO2.
Thanks Raymond but I guess I should have mentioned that I am running Co2. So I am going for high light range, I just don't want to spend that $379 unless I need to. The difference between the BML and the Current are night and day (no pun intended) so I view the Current as pretty much irrelevant at this point. The reason I am thinking I might need another is that the lady at BML told me I would need 2 of these dutch lights for my tank to achieve high PAR levels. Maybe to sell another light, or maybe because I actually need it. I'm just not sure.
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Old 02-28-2015, 12:32 AM   #7
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Quote:
Originally Posted by Rainer View Post
And the plants there will lean in because of it.

Starting to notice this. I'll have to find a way to mitigate this.
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Old 02-28-2015, 01:55 AM   #8
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Even offsetting them probably won't work. I have offset 24" bulbs in a 30" fixture and still have that problem.
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Old 02-28-2015, 02:23 AM   #9
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I don't think Cara would tell you to buy another light just to make a sale.

She has been exceptionally honest with me when she could have charged me extra several times or just not done anything at all.

They seem to be a very honest company and I don't say that about many that I've dealt with.

FWIW, I had a Current while my BML was down. It barely reached the bottom of the tank at 18" deep. My plants were dying. I sent it back.
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Old 02-28-2015, 10:13 AM   #10
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the reason for adding another light in your case would be beneficial is because one strip of leds will not cover from to back adequately you add more leds for coverage. intensity will increase where the leds focuses light overlaps but it only make up for missing emitters directly overhead. there is a reason 3 of the bml strips are recommended over most tanks. your medium light plants need to be directly underneath the fixture depending on depth of the tank. lower light plants within 6 inches of it and not much beyond that. obviously you can raise the leds to increase the circumstance of coverage but you are also reducing the intensity. you can raise a 3w led unit but you probably don't want to be raising a 1w or .5w led fixture to much.

if the leds are not using optics you can generally expect a 120 degree spread. take a protractor and measure 120 degrees in a circle down from the emitter. keep in mind only directly under the led will get the high par reading. once you get to the edge of that 120 degree circle (60 deg from center) your par will be 10% of the peak number underneath. obviously this wouldn't be enough so another, and another emitter is added for coverage.
optic take that light and focus it so instead of a wide flood light pattern its turned into a flashlight and even tighter a laser beam.
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