# PAR values for low, medium, high lighting



## rcs0926 (Jun 14, 2013)

I'm a little confused as to what constitutes low, medium and high lighting when it comes to PAR. For the past couple of months, I've been using ranges provided by Hoppy's thread:

http://www.plantedtank.net/forums/showthread.php?t=184368

Low light - 15-30 micromols of PAR - CO2 is not needed, but is helpful to the plants
Medium light - 35-50 micromols of PAR - CO2 may be needed to avoid too many nuisance algae problems
High light - more than 50 micromols of PAR - pressurized CO2 is essential to avoid major algae problems

However, it's clear that others use different ranges to define low, medium and high light. I'm interested to know if the values posted above are generally accepted by members of this forum of if others use different ranges. Thanks.


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## jpappy789 (Jul 28, 2013)

Definitions like "low" "medium" or "high" are going to be subjective and always will be even since we were using wpg as a measurement, just good estimates to follow for suggestions for plants that have a good chance of doing well in your tank provided their other needs are taken care of. 

I mean, I don't think a plant that was growing at 50 mmol is going to think "oh crap, now there's only 48 mmol PAR now I can't grow because I'm a high light plant". There's going to be gray areas at the edges of these ranges though where YMMV. I think you're better off trying things out yourself, seeing what works and seeing what works for others with similar conditions. Just my take on this though...


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## rcs0926 (Jun 14, 2013)

jpappy789 said:


> Definitions like "low" "medium" or "high" are going to be subjective and always will be even since we were using wpg as a measurement, just good estimates to follow for suggestions for plants that have a good chance of doing well in your tank provided their other needs are taken care of.
> 
> I mean, I don't think a plant that was growing at 50 mmol is going to think "oh crap, now there's only 48 mmol PAR now I can't grow because I'm a high light plant". There's going to be gray areas at the edges of these ranges though where YMMV. I think you're better off trying things out yourself, seeing what works and seeing what works for others with similar conditions. Just my take on this though...


I hear you. In actuality, I was confused because of differing PAR values given for the Finnex Ray 2. Finnex PAR chart shows lower values in comparison to the readings that Hoppy did. Since getting back into the hobby, I've just relied on Hoppy's numbers in his "lighting with PAR" thread. When some posters were claiming that a 24" Finnex Ray 2 gives low light at a depth of about 24", I was confused because Hoppy's thread shows that the Ray 2 gives medium light at that depth. That's where the confusion was, which is why I asked the question about PAR ranges. As it turns out, my understanding of the Ray 2's PAR values was off in comparison to the official Finnex PAR chart.


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