LED Lights and a Planted Tank
I posted this in response to another thread and was asked to post a new thread, so here it is...
I spent quite a while trying to figure out how to rate LED lighting and thought I'd pass on this information.
Although LED's are rated in wattage in the same fashion as "normal" lighting, that value is of inconsequential use when attempting to determine the value of a light for a planted tank. The same can be said of the lumen values. Instead, the value commonly referred to for this function is "PAR" (or, photosynthetically active radiation). In simple terms, PAR refers to the amount of light that can actually be used at a given depth. PAR can be measured for readily using a PAR meter, but these meters are rather expensive and most aquarists will be unlikely to have one available. As a result, reference to the manufacturer's published data is your most likely source of this information. Note, however, that not all (or even most) manufacturer's provide this information.
There is currently a vast amount of information related to PAR values and determining the level of light, including various charts and measurements, available around the web. For my purposes, I agree with the information I've found elsewhere which refers to a PAR value between 10-30 as "low light," 30-80 as "medium light," and 80-120 as "high" light."
It should be noted that these values are at a given depth. As such, a light that has a PAR value of 120 at 12" will not achieve that at 18" or 24". Light diffuses rapidly at depth and the PAR value may be reduced by as much as 50% or more even by only adding 12" of depth. As such, you must determine the PAR for the depth you'll be working at for the reference to be truly useful.
There are two principal problems I've noted with LED's. One, they tend not to penetrate enough for good growth at lower levels. As a result, you'll have plants that are doing fine near the surface, but that may wither or die at lower levels (this is particularly true for plants that are not primarily oot feeders). Two, they tend not to diffuse well and so you end up having some very bright spots in your tank, but also very dark spots. Plants in the shadows will not grow as well, and so you must arrange them to make use of the light pattern.
As to the LED's you might find that are stocked at your local Big Box store or LFS, they may be fine for a small tank that is fairly shallow, but I suspect they will end up being insufficient in most cases. These inexpensive LED's tend to use low wattage (I.E., .06) bulbs that are highly focused. As such, their PAR value is substantially low and they are very much like spotlights. In addition, the color temperature may be very high (and is likely not indicated by the manufacturer) and less than ideal for plant usage. They may be great for appearance, but are of less use for growing plants. In contrast, they are inexpensive enough that it might be worthwhile to experiment with your setup.
With the proper optics over the LEDs you can get plenty of depth,I prefer 90 degree optics over 1 or 3 watt LEDs. This will give you at least 2 feet of punch if you are running 3 watts.
The coverage is obviously determined by the spacing of the LEDs and or the degree of Optics,Think Kessils with one optic and tight spacing and Reef Star with 100 LEDs and 100 Optics,Both cover 2 square feet but are completly different in light delivery.I guess what I am getting at is you might have not tried out the "good" LEDs units as there are many out there. Even the DIY ones are pretty good In My Opinion.
I was never a fan of the bogus watts per gallon rule , what kind of lighting are you using\testing? Marineland or Wave Point by chance? Those fit the bill you have described.
Sorry I just saw that you are talking about .06 watts , yes those will not get you too far in the penetration department and without a proper mix of spectrum your PAR will be down as well.
I tried a number of different "inexpensive" LED's. I had the most success with the Marineland "Hidden" LED lights.
Freshwater Saltwater Reef Aquarium LED Lighting System | Marineland
A combination of 2 of these, along with a fluorescent hood, resulted in sufficient light to grow low to medium light plants. They did not thrive, mind you, but they grew.
I looked to other fixtures that seemed appropriate such as the Marineland Single or Double Bright and the Fluval Ultra Bright, but didn't want to start blindly spending money. I also wanted to stay with LED's, but didn't want to drop $600 or more on some of the high-end fixtures I was finding.
It was at that point that I started learning about PAR as I was getting aggravated by the volume of forums and internet blogs simply reverting to the old "2-3 watts per gallon" rule. The PAR on my combination of LED's and fluorescent was 15-20 at best (at 18" depth). That explained why my Hornwort and Anacharis were wilting at lower levels while sprouting upwards. It also explained why my Swords and Crypts were alive, but not really growing.
So, after researching various options, including BuildMyLED, Finnex, Marineland, Current, and several others, I settled on the Marineland Aquatic Plant LED. It provides a PAR value of approximately 120~ at 18" and an appropriate spectrum of white, red, and blue light. Now, my issue is too MUCH light and proper balance is required between light, ferts, and CO2.
That's a "problem" I'm happy to have. ;-)
Thats a pretty good PAR rating at 18 inches,any pics?
Looks really good,as does your tank layout with the clean and open spaces. Are all the plants in this tank grown with the current LED you have? If so that might be a winner if the price is comparable to some other brands, I will look into it at my local fish store here soon.I love getting new lights :)
The other fixture I strongly considered was a Dutch Planted fixture from BuildMyLED. They're comparable in price, but have a somewhat lower PAR rating. However, they are full length and include a dimmer as an option. In contrast, they have no "moonlight" setting or timer. I really like the blue and use it for a few hours in the evening before the tank goes dark. So, all in all, I'm very happy with the Marineland fixture.
Thank you for the review of the light :-) It is a good thing to share some of your insight seeing as the selection is head spinning in the light department. I test out many lights but mainly over corals so its nice to get a different view. I will be posting some goodness in the near future,including some lighting,so I am sure I will be seeing you around.8-)
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