Finnex FugeRay 36" LED or something that looks just like it.

[tug]

I have the Finnex FugeRay 36" LED and it bothers me that when I recorded the PAR values under my light they came out higher then what I've been reading elsewhere. This is a good thing but it casts doubt on my PAR readings and I hate that.

To the naked eye it's bright, significantly brighter then I thought it would be. The design is ok. I don't like the docking mounts but otherwise it's a sleek, sturdy design and it's bright. After reading Kris's article on the Current's Satellite, I now use both of these lights and am much happier. The Satellite gives me extended viewing and provides for better color rendition and the FugeRay gives me 6 hours of light for a midday burst.

Still, if there is anyone in the DC area that has the PAR meter and you would like to stop over for a beer I would love to have another go at this, bring it on. I can show you my two tanks, we can test “photosynthetically active radiation” and talk plants.

So, these are the PAR values I recorded.

The 35 gallon tank I tested was filled with water but other then the substrate it was empty. The tank's footprint is 30" by 12" and it stands 23" tall. I cleaned the glass on the tank and took the readings in the darkness of my basement.

I recorded 70 mmols of PAR at 14 inches and 58 mmols PAR at 20 inches . It might be important to note that this was a 36" light sitting on top of a tank only 30" long.

The other tank is a planted, 30 gallon tank. Its footprint is 36" by 12" and it stands 16" tall. This tank is also in the basement. All the other lights were turned off during the test but the glass was not cleaned this time.

I recorded, 89 mmols of PAR at 8" from the light and 50 mmols of PAR at 15 inches.

Some of the deviance might be due to the tanks themselves. In aquariums, the air-water interface slightly focuses the light and refracts it back towards the center of the tank. The glass sides of the tank also reflect light back into the tank. The dirtier the glass or the more plants in the tank and the light reflected back into the tank is decreased to some extent.

This might be why the PAR values for the 35 gallon tank were higher. But, both of my readings are higher then what I see reported, 40 PAR at 14" from the Finnex Fugeray LED 30" long. Would Aqua Vibrant have sent me the wrong light?


Lighting an Aquarium with PAR instead of Watts, Hoppy
http://www.plantedtank.net/forums/showt ... p?t=184368

[tug]

I sent an email to Vaughn (Hoppy). I gave him my results and asked for ways to improve the accuracy of our PAR readings. The email was pretty much like the post above except I left out all that stuff about air-water interface. Vaughn has forgotten more about this stuff then I will ever know. Anyway, this was his reply.

All LED lights, in a long bar like that, give more PAR the longer the light is, unless there are optics added to each LED.  I'm not sure that you can assume that if a 36 inch long light is on a 30 inch long tank, that you will get the PAR shown for a 30 inch long light.  Some additional light will still come through the end glass, raising the PAR to near what you get with the whole 36 inches in use.

It is hard to get a really accurate PAR reading.  I am convinced that the best we can do is to get within 10% of the true PAR.  If you don't use a fixture that lets you hold the sensor without having you arm/hand in the tank, you lose a lot of accuracy.  You can get too high readings, from reflections off your arm or too low readings if your arm blocks light from part of the length of the bulb/LEDs.  For that reason our club PAR meter has a acrylic strip attached to the bottom of the sensor, with an acrylic rod extending up from the other end of the strip, so we can hold the sensor in place without having our arm or hand in the water.

[krisw]

Good information Mike. Since our club PAR meter has a long cord, I've fond it effective to anchor the cord down in the tank with a spare rock so that my arm doesn't need to be in the tank at all.

[tug]

Thanks Kris,
I can look around for the diy. the acrylic rod sounds like a good idea and easy to make. Some GWAPA members are pretty darn good at building stuff, more so then I am.

As for me, I'm happy with the PAR readings I got. They're not as far off as I first thought. If anything the true readings were possibly higher. At the very least, I can say the Fugeray provides high levels of PAR for most tanks and wouldn't hesitate to recommend it with elevated CO2 levels. I don't know about a tank any wider then 12" but I got very little variation in PAR moving the meter 5" out from the center. So, one of these lights will spread the light out evenly in narrower tanks.

My only caution might be that most people will not like the quality of a light rated at 7,000K. I don't have a lot of experience using lighting or using different color temperatures to justify this but 7,000 K seems to wash out some of the color in my tank. It does have 12 actinic LEDs that when there run at the same time, helps a little. This is why it may be a while before people start to give away their T5 fixtures. They still provide better color options for viewing. And, after all, that's what it's all about - not just PAR.