Useless with most aquarium lighting, By Wendell on 9/22/2016
Wendell wouldn't recommend this product to a friend
The meter is not calibrated to measure underwater or for use with multiple types of artificial light. It was designed to measure sunlight as well as --SPECIFIC-- artificial lights (one at a time). The deviations are pretty big and you cannot use it to determine PAR on your tank.
There are a set of conversions for different lights. Halide -3.7% (who knows what color bulb) , white LED lights -4.6% and another one for blue LED -12.7%, and several others (most have no wavelength). But, If you run multiple colors of LED lights or combination of different lights, like T5 and Halide, there will be no way to convert the numbers you see on your meter. You may be able to get a consistent reading, but it will not have much to do with PAR.
If you plan to use it underwater, there are geometric and immersion effect correction factors to multiply, and a conversion calculator you can download. It is not a consistent number like 22%, it is a formula that you need the calculator for. You will need have your computer out so you can enter the meter reading, the water depth (in Meters) and distance from light source to get the corrected readings. Then you could go on to enter the correction factor of your lights if you are using straight Halide or specifically cool white fluorescent T5 bulbs.
Remember that this meter will only measure PAR or PPFD, not spectrum. Your reading is for total light between 400 to 700 nm. It is not a useful tool to check your lights for spectrum shift from ageing, and is going to read incorrectly if you are not able to apply a color correction factor.
The meter may be useful to you if you are working at a specific depth in an aquarium. You could move it left and right and get an idea of whether it is getting lighter or darker. Not really useful.
Get what you pay for By zega on 5/13/2015
zega would recommend this product to a friend
I am the lucky one having 2 Li-COR quantum sensor units, bunch of photospectrometers building kinetic flurimeters & stuff (check photosynq.org)...
Now i compared it with Li-cor and i.e. when using 660 monochromatic light source (LED-actinic) or blue errors are huge exceeding 80%, it is calibrated for sunlight spot on, but for FL it is 10% off (i have done correlation for FL with LI190/LI-250 f(x)=0.904-5.94
for that reason i have printed spectral sensitivity curve and correlation and keep that in the box all the time.
So spectraly it is meh 2-3stars, linearity is nice, it is small practical, looks good (better then Li-cor looks and functionality are great) waterproof (great)...
Very nice and compact By Reef&Frag on 12/10/2014
Reef&Frag would recommend this product to a friend
I have been very happy with this unit. Very simple and easy to use. After watching some videos online it seemed like it worked better as a relative measurement than a precise reading. Overall very happy with my purchase.
Great for PAR By NE Patriots Fan on 4/2/2014
NE Patriots Fan would recommend this product to a friend
Very good if you want to get serious about your lighting. This gives you great results and is easy to use. PAR is very important if you have a reef tank. This is a good meter to use to see where your lights stand. I bought one 8 year ago and still use it today.
Nice unit By Chicago on 3/25/2014
Chicago would recommend this product to a friend
I use this to track loss of light not necessarily the exact par. Works as described. Might want to research it's ability to read all blue led
Great product By ReefDVMs on 5/13/2013
ReefDVMs would recommend this product to a friend
When switching over to LEDs and or moving coral via one system to another i have found this device to be very valuable, works well and waterproof sensor is prefect