# What par is considered low light...



## Craigthor (Sep 9, 2007)

I am dosing EI low light on a daily basis via a dosing pump setup usign RootMedic Liquids.


----------



## diwu13 (Sep 20, 2011)

I think it's something like:
"10-30: low light.
30-80: medium light.
80-120: high light."


----------



## FriendsNotFood (Sep 21, 2010)

Not to highjack the thread but is that number listed for directly below the light? Cause I have par 30ish under the light but by the bottom/sides of the tank it drops down to 1 or 2.


----------



## diwu13 (Sep 20, 2011)

FriendsNotFood said:


> Not to highjack the thread but is that number listed for directly below the light? Cause I have par 30ish under the light but by the bottom/sides of the tank it drops down to 1 or 2.


Both of you should read through all the posts by *i4x4nMore *here: http://www.plantedtank.net/forums/lighting/85667-par-data-spiral-power-saver-bulbs-2.html#post834956

It's really helpful and will answer all your questions! He even made his own figures haha! Like the one below:


----------



## Craigthor (Sep 9, 2007)

So it looks like 40-70 is low light according to his thoughts...


----------



## FriendsNotFood (Sep 21, 2010)

Hmm... this is very different from Hoppy's chart... on his chart, low light is 30 and below.


----------



## jcgd (Feb 18, 2004)

Hoppy, Tom and others say around 50 par should be sufficient to grow most anything with co2 and proper conditions. So instead of low/med/high I'd aim for adequate and if you have all plants with lower light needs I'd say a little under is fine.


----------



## Hoppy (Dec 24, 2005)

We are all learning as we go, as far as what "low", "medium" and "high" mean for lighting. In my opinion (today) low light is around 15 to 30 micromols of PAR. Medium is around 40-50, and high is more than 60 or so. I have read in another website, which I don't recall, that 60 and above is high light. I know that people have had success with around 15-20 with non-CO2 tanks. And, 40 to 50 is adequate for growing just about every aquatic plant we would want to grow, assuming we have good CO2. All of those numbers are as measured at the substrate. Since the PAR goes up as you get closer to the light, a low light tank will have a lot more than 20 micromols of PAR up near the water surface.

Another way to look at PAR and light levels is to measure the PAR right at whatever plant you are concerned with, and evaluate that reading as low, medium, high, etc. That is a whole different set of numbers.

I am only concerned with how to pick the "right" light for a specific tank, and for that all you can do is look at the PAR at some standard spot in the tank, which I think should be the substrate level (maybe an inch above it). You can't do anything about what the PAR is at other locations in the tank, except by starting with a light suspended at a different height above the tank, or by using a spread out group of lights.

Life was so much easier when all you had to do was read the wattage of the bulb and divide it by the gallon size of the tank. Of course you really had no way of evaluating what that meant, but many people were happy with it. It is a lot like trying to specify CO2 concentration as a certain bubble rate. Simple, but meaningless.


----------

