Light Meter

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I'm gald you asked. I've been looking at that item for a couple of months now and have wondering if it is worth getting or not.
 
Ok, maybe I'm behind on some bit of knowledge here. What would be the point of measuring the 560nm output of an aquarium light?
 
Some species of aquarium fauna (and flora for that matter) are extremely picky about the amount and wavelength of light they live in. Though I am not a saltie, I understand that some corals and things like that are especially picky.
 
I also wanted to use it to test how long different bulbs will last.
 
Ah okies, I stick with pairs of bulbs myself. Since I put them in 6 months apart I can always see when one gets dim and swap it out. Wouldn't work so well if they're all different types of bulbs though.
 
Yeah plus the spectrum will shift as they get older, but you really can't tell with the human eye.
 
I'm not tracking with this light meter. Where does Lux fit in with PAR or are they interchangable? Also will the Lux value be interchangable with say 10,000k bulbs??? I'm guessing there is a chart or something that will provide conversions???
 
Lux
The intensity of light that impacts a surface is described by an international unit of measurement called a "lux." It is the metric measurement similar to a foot-candle: 1 foot-candle equals 10.7 lux. The level of intensity on a natural reef with clear water will average about 20,000 lux at a depth of 15 feet, and 10,000 lux at 30 feet. Knowing where an organism lives in nature will give you an idea of the light intensity that will be required to maintain that organism in an aquarium. Lux meters are available and are relatively inexpensive, and can be used to both check your lighting for the intensities that are required, and to determine when bulbs in the system need to be replaced.
 
Officially PAR is the 400-700nm range. Lux is supposed to be total radiation at a distance of one meter. Usually though it's calculated based on measuring some specific wavelength around 550-570nm since that's where the human eye is most sensitive, and assuming that the other wavelengths are putting out progressively more or less power.

Unfortunately modern light bulbs don't play by the rules. They put out varying amounts of light at defined wavelengths. Then of course when the spectrum shifts, it's hard if not impossible to tell by looking at it without some direct comparison. You can either use a lux or quantum sensor to compare a reading, or you can compare to a brand new bulb if your eyes are good enough.

Basically all of the light scales are work arounds to avoid having to copy down a spectrum graph. The same way decibels are used to describe volume without telling you pitch.

Basically they are trying to find a simple way to compare these with one number:
SPD.png
 
Ok...way over my head. I'll just stick with replacing my MH bulbs every 6-8 months. I need to find a "light bulbs for dummys" book somewhere.
 
check out the new tubes from Longiotti LEDs
then there will be no need to replace bulbs.
I have a 90 gallon tank and I was running VHOs. I was replacing my bulbs twice a year. I got these and the color output is amazing. no need to replace bulbs and they consume half the electricity of VHOs. the blues are amazing, I love these things.
 
Well I don't know what I was right about this thread has completely confused me with lux and all that.

BRK uses a PAR meter to determine light intensity at different depths in the tank. I do know that it is best to use the PAR meter when your pumps are running as they normally would. By doing this you will get a more accurate idea of what kind of PAR you are getting at any given depth in the tank. The trick is to watch the meter for a few minutes and get a "high" and "low" reading and go with an average. If you shut your pumps off and the surface is calm you will be getting false readings because the ripple does make a difference on how the light penetrates the water.
 
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