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Discussion Starter · #1 ·
I've been growing aquatic plants with some success for more than 20 years. My tanks have been low tech and soil-based, with no added nutrients except fish waste. And light. And that's the source of my question.

I'd been using about 2 watts per gallon of T12 and T8 fluorescent tubes, usually in shop light fixtures. Everything was rosy. Then the tubes and the fixtures started to die, and replacements were hard to find, then impossible. I bit the bullet and decided to buy a LCD fixture for my 29. I got a recommendation and bought one about 3 years ago. The price was quite high but the light was amazing. The plants did great!

But the price was too high to justify buying LCD's for my smaller tanks. I made do with various combos of screw-in LCD bulbs and desktop fixtures, but this was barely acceptable. Then I recently found some LCD fixtures in a Pets-whatever at very reasonable prices.

So after all these words, here are my questions:

1. With tubes, I knew that 2 WPG would work. How is LCD lighting measured? By the number of LCD's in the fixture? By lumens? PAR. if it's available (but there are so many variable . . )?

2. With the tubes I would chose a Kelvin of 5000 - 6500 with a CRI in the mid-90's. What
metrics are used in the LCD world?

3. It could be my eyes, but it seems to me that the LCD's don't illuminate the sides of fish as well as the older bulbs. Do the tubes produce a more diffused light? Are the LCD's more point-to-point, like lasers?

Thanks for your help and your patience. <g>

Bill
 

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LEDs (light emitting diodes) are point sources of light. Each of them alone is a pretty weak light "bulb", but most LED aquarium lights use dozens of them spread out over a large area. Unlike fluorescent lights they don't need reflectors, and each tiny LED produces a cone of light about 120+ degree cone of light. So, they cover a lot of area with light coming from all directions. Many manufacturers of these light fixtures also measure the light intensity from them at various distances, expressed in PAR dimensions, photons per square meter per second. Look for the intensity at the distance your light will be from the substrate. If that is 20-40 it is low light, 40-50 or 60 is medium light, and above 60 is high light.
 

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LCD colors are measured in kelvin as well. I think naturally they’re 5500k. For different colors, the lens is coated with a certain color.
 

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LCD colors are measured in kelvin as well. I think naturally they're 5500k. For different colors, the lens is coated with a certain color.
Color temperature doesn't really apply to LEDs since they produce much of their light in very high peaks at specific wavelengths. Different phosphors are added to the LEDs to adjust their light spectrum so it is more useful, and that can make them provide mostly red, blue, etc. colors. That lets the manufacturer rate their LED lights by color temperatures comparable to fluorescent lights. Good LED lights have some very red diodes, some very blue diodes, and a good mix of other colors, so the light they generate contains most of the wavelengths of light needed by plants, plus a pleasing appearance for human eyes.
 

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Discussion Starter · #5 ·
Thanks for your responses!

Please pardon my obtuseness.

Are we saying that all Kelvins in the 400 - 700 nm range produce about the same PAR values, all other things being equal?

Would the answer be the same for both LED and tube-generated light? Why?

Since par diminishes with the distance from the light source, what would be the difference between a a fixture designed for a deep tank and a shallower one, given the same footprint? More LED's? More voltage?

Thanks again,

Bill
 

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Are you sure the various colors are from the coating? I read that some colors of diodes are kind of recent and have different chemicals. I could and might be totally wrong
 

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Thanks for your responses!

Please pardon my obtuseness.

Are we saying that all Kelvins in the 400 - 700 nm range produce about the same PAR values, all other things being equal?

Would the answer be the same for both LED and tube-generated light? Why?

Since par diminishes with the distance from the light source, what would be the difference between a a fixture designed for a deep tank and a shallower one, given the same footprint? More LED's? More voltage?

Thanks again,

Bill
"Kelvin" is the absolute temperature in the Celcius temperature scale - what used to be Centigrade degrees. It is the name of the absolute temperature scale. A Celcius degree is the same as a Kelvin degree and is a measure of temperature. The wave length of light is often measured in nanometers or "nm". 400 to 700 nm wave length is the range of wave lengths, or colors, of light that plants can use for photosynthesis. When light sources are given a Kelvin temperature it means that a black body at that temperature would radiate light with about the same intensity vs wave length as the light source produces.

Light fixtures are not designed for any specific shape of aquarium, other than that their length is always intended to be equal or less than the aquarium length. If a light is suspended high above the aquarium the light intensity will vary much less over the full height of the aquarium than for light fixtures sitting right on the top of the tank. But, with most LED lights, the large angle cones of light from each individual LED will cause a lot of spill over light with the light high above the tank.
 

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Discussion Starter · #8 ·
I was using "Kelvin" in the context of growing plants, where the term is essentially synonymous with "color temperature". In the past, a Kelvin of 5000 to 6500 degrees was considered best for most aquatic plants. The sun at the equator approximates that. Are we saying that doesn't matter with LED's?

To restate my question about light and tank depth, how does one determine how many LED's a tank a tank needs?

It would seen that a deep tank would need more light that a shallower one. Some fixtures contain more LED's than others with the same dimensions and they'd then seem to produce more light at the bottom of the tank, but do they?

Thanks again!

Bill
 

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I was using "Kelvin" in the context of growing plants, where the term is essentially synonymous with "color temperature". In the past, a Kelvin of 5000 to 6500 degrees was considered best for most aquatic plants. The sun at the equator approximates that. Are we saying that doesn't matter with LED's?

To restate my question about light and tank depth, how does one determine how many LED's a tank a tank needs?

It would seen that a deep tank would need more light that a shallower one. Some fixtures contain more LED's than others with the same dimensions and they'd then seem to produce more light at the bottom of the tank, but do they?

Thanks again!

Bill
Fluorescent bulbs have long been categorized as "daylight", "warm", "cool", etc. and more recently by a color temperature, one of which is 6000-6500K. But, even those bulbs didn't really come close to matching a black body at that temperature, because fluorescent bulbs have several high peaks in their spectrum, instead of a continuous, smooth spectrum. Plants don't need any specific color temperature bulb. They do need significant light in several parts of the light spectrum, whatever type of light source it is.

There is no specific equation that I'm aware of for determining how many of what type LEDs are needed for various sizes of tanks. When I was building my own LED lights I measured the light output of single LEDs, and, for tape mounted LEDs, the light output for various rows of tapes of specific types. And, I was able to use that to get a pretty accurate guess about what any group of LEDs would produce.
 

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Get something really strong but make sure you have a good dimmer, etc and turn it down to whatever turns out to be appropriate. :)
 

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One very valuable characteristic of the tape mounted LEDs is that you can get a very cheap dimmer that lets you step the intensity down from maximum to a much lower intensity, with a click of a button. Or, if you are knowledgeable enough, you can use a computer to program the intensity vs time.
 

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I bought a Yescom 48" fixture that has 156 diodes. Now,that's the most of any brand except Fluval 3.0 with 220 or so. But! the Yescom I paid $47 give or take,and the Fluval sells for over $200. What's really interesting is that I also still use flourescents with it using Marineland I think it is more neutral bulbs. What I notice is that when I shut off all the diodes but the blue in the evening? I get a look very much like old gro lux bulbs...greens and reds really pop.
I was posting about yescom months ago on youtube...then I find they have stopped making them in 48". I thought it would have been their best seller. Back to the drawing board if it ever goes out. 7 months so far and its fine..feels cool to the touch,but I also use a fan to keep the fishroom from becoming too humid and stagnant.
 

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Discussion Starter · #13 ·
Get something really strong but make sure you have a good dimmer, etc and turn it down to whatever turns out to be appropriate. :)
That makes a lot of sense, unless one is trying to maintain a low tech environment that was quite content with 2 WPG's of T12 light. Even when throttled down, the LED's produce far more plant growth than I want, and if I further dim them, I can't see the fish very well.

Maybe LCD's don't work in low tech tanks?

Today I stopped at a Pet's-whatever to look at the LED's. They had several Aqueon models. None had anything like PAR, Kelvin, or CRI on the packages.. The closest they came was using adjectives like "Cool White" and other non-standard terms.

So apparently there isn't any objective way to select LED lighting.

Thanks, all!
 

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Over my smaller Walstad tanks (20 and 40 gallon) I use Finnex Stingray fixtures. Strangly for LED fixtures they have a relatively narrow beam angle. Over a wide tank like a 40 breeder, I need two. On my 75 Walstad tank I have a Finnex Planted Plus. It has no dimmer, and it really needs one.

I've been very happy with Finnex, with the exception that their power supply assemblies are not very reliable. Apparently this is a problem with many LED brands. For the Planted Plus you can buy a replacement power supply that just plugs into the fixture. But replacements aren't available for the Stingray, and since it isn't modular you have to buy a replacement that matches input/output of the original and hard-wire it.

For other smaller Walstad tanks, I've had good results using an old screw-in incandescent fixture with hardware store LED "bulbs". Here are some I got from Amazon: https://www.amazon.com/gp/product/B074T8TVM8/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

We recently bought some cheap 48" LED shop lights to use for. . .shop lights! They are very bright with good color rendition (to me). I plan to borrow our club's PAR meter to test them, and I'll post results.
 

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Discussion Starter · #16 ·
When I next buy a LED fixture, I'll get Finnex. Thanks!

I am using the screw-in LED bulbs on 2 10 gallon tanks. The results are not great, but maybe for reasons other than light.

I'm using Phillips, 16 watt "same as 100 watt" bulbs, 1600 lumens, "appearance" 5000k. I'm using 1 bulb per 10 gallon tank. Does this sound OK?

Thanks.
 

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I'd been using about 2 watts per gallon of T12 and T8 fluorescent tubes, usually in shop light fixtures. Everything was rosy. Then the tubes and the fixtures started to die, and replacements were hard to find, then impossible. I bit the bullet and decided to buy a LCD fixture for my 29. I got a recommendation and bought one about 3 years ago. The price was quite high but the light was amazing. The plants did great!

But the price was too high to justify buying LCD's for my smaller tanks. I made do with various combos of screw-in LCD bulbs and desktop fixtures, but this was barely acceptable. Then I recently found some LCD fixtures in a Pets-whatever at very reasonable prices.

So after all these words, here are my questions:

1. With tubes, I knew that 2 WPG would work. How is LCD lighting measured? By the number of LCD's in the fixture? By lumens? PAR. if it's available (but there are so many variable . . )?
They are measured by all of them BUT "PAR" or more correctly PPFD is the preferred which comes from either a manuf. chart or a measurement made w/ a quantum meter.
Generally one can guess just like in the old days..
Start w/ 1 W = 2W tubes for standard tanks (not too deep not to shallow).. Long story why this has some validity.

2. With the tubes I would chose a Kelvin of 5000 - 6500 with a CRI in the mid-90's. What
metrics are used in the LCD world?
CRI is more for looks though high daylight CRI i.e 6500k 95CRI assumes a broad spectrum w/ few missing or low wavelenghts but that is a bit dependent.
CRI is an average of at least 8 color swatches but different swatches can have different numbers but add up (average) the same. In other words 95CRI can look different between bulbs.

3. It could be my eyes, but it seems to me that the LCD's don't illuminate the sides of fish as well as the older bulbs. Do the tubes produce a more diffused light? Are the LCD's more point-to-point, like lasers?
Yes LED's are more point sources. Commonly each LED is lensed at 120 degrees where tubes slosh at 360 and rely on reflectors to focus it. That does come at a small price of less focused light on the bottom
but more diffusion.. i.e lower "PAR" better spread.
If your fish have dulled sides you can probably improve that by raising your light a bit.
You'll get better and more even bounce off the glass adding to their illumination.

Ideally, get an LED that can produce the "shade" you want w/ 2W per gallon BUT be dimmable.
you prob won't use all the power.
LED watts not "equiv watts"
Set it up so all light enters at the surface.
3" off the water line a single row of LEDs will cover front to back about 10" of surface @ a lens of 120 degrees.
4" up 14" front back.
Keep in mind the higher up the less PAR at the substrate though.
You shouldn't have issues growing things .

Obviously the more light the more need of the other nutrients (ferts and CO2) or you will have issues.

Last thing.. White LED's are really Blue LED (Royal blue common,Violet exotic) w/ a phosphor coating.
This coating is usually just a yellow or green broad phosphor making it look white.
Low K LED's may add a red phosphor to make that low K.
Violet based pumps use RGB phosphors (just like tubes).
high CRI white LED's add ancillary phosphors added to yellow to boost the red/cyan/reg blue that is in short supply in the average low CRI white LED.
Low CRI white fixtures can add RGB monochromatic diodes to boost contrast and look. This will usually boost the CRI away
from to the 70-80-ish of cheap white diodes.
Do you remember when tubes first came out w/ bad CRI? Ugly green tint. Same thing happened in LED's
A RGB only light can look punchy, work really well but still will lack in certain spectral components.
Plants adapt..
 

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When I next buy a LED fixture, I'll get Finnex. Thanks!

I am using the screw-in LED bulbs on 2 10 gallon tanks. The results are not great, but maybe for reasons other than light.

I'm using Phillips, 16 watt "same as 100 watt" bulbs, 1600 lumens, "appearance" 5000k. I'm using 1 bulb per 10 gallon tank. Does this sound OK?

Thanks.
May be placement, may be too much light not enough ferts/CO2.
Light should be enough for a 10 gal.
see Hoppy and my above preaching.. ;)
 
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