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LED flood lights for planted aquariums

Jake L.

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Here is the summary first,

  • Hardware store LED floodlights are inexpensive but weak in the light needed for plant growth
  • Horticultural LED floodlights are expensive but strong in the light needed for plant growth

After reading your post above, I measured the output of a LED floodlight I have in kitchen. I have a light meter that measures intensity across the spectrum of light. This is the LED floodlight in my kitchen.


This produces nice warm visible light that I prefer, but it is lacking in those parts of the spectrum that plants need for growth.

I also measured sunlight with the meter which also measured the photosynthetically active radiation (PAR) which is just a fancy word for measuring the spectrum of the light that plants can use to make food and grow.

This is what sunlight looked like this morning.


The big blue hump on the left and the big red hump on the right are the part of the spectrum that plants can actually see. What that chart also shows it that we (humans) like which is the middle greenish yellow part of the spectrum.

We humans perceive that middle part where red and blue and green equally combine as 'white' light, or sunlight. Plants don't care about that part, they are interested in only the blue part and the red parts.

So when you buy an LED floodlight, what you get is a lot light that doesn't grow plants but looks good to you.

To get a LED floodlight that grow plants, you need to buy a specially designed horticultural LED light that is rich in the blue and reds plants need.

Here is the spectrum of a Kessil a360x LED floodlight tuned to grow plants.


To our eyes, this would be blue plus red, so we would perceive this as purple. Not very pleasing. So Kessil makes a version of the a360x tuned to grow freshwater plants, but still be pleasing to our eyes. This is the Tuna Sun spectrum.


And yes, I use Kessil three a360x's to light my deepest aquarium (the other thing in the photo is my automatic feeder),


and I like them and would buy them again, but I paid through the nose to get these.

So in summary,

  • Hardware store LED floodlights are inexpensive but weak in the light needed for plant growth
  • Horticultural LED floodlights are expensive but strong in the light needed for plant growth




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Just now, Wisnasky-tank said:

So what’s the cheapest low level horticulture light that you can buy? You said that cost you a pretty penny? Just how pretty of a penny are we talking are you saying if you use anything but those your plants not gonna truly thrive? 

Not saying that at all. I have used metal halide lighting on this aquarium and that is relatively cheap, it is just noisy and hot.

Plain old dirt cheap florescent bulbs work really, really well for growing aquarium plants. And personally I use inexpensive Finnex Stringrays LEDs for all of my smaller aquariums. They are super durable (I can't tell how many times I have dropped them in water or on a concrete floor and never once has one failed), and you can't beat the price.

But if you want LED floodlights, that is pendant lighting that produces a serious amount of light and is geared towards horticulture use, then you have left the realm of cheap.

The lighting for my biggest aquarium which is 3 feet deep came in at roughly $500 per light, and I am using 3 of those lights on the big aquarium. It is one of those areas in life where you get what you pay for.

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I use GE 32 watt balanced spectrum grow lights, they work great, 28$ if they are on sale + 8$ for a fixture.


For tanks that need two or them, like my 40 breeder or my 50 Rubbermaid pond, I use 1 GE and 1 Phillipps 250 watt equilivelent flood light.


Here is one of the GE lights, I have it about 2 feet above a 40 gallon tuff stuff, provides pretty decent light:A048C905-1769-403E-8EEF-9468E28FD6CD.jpeg.4583f8637f4aaef282a62661b2e5d253.jpeg


I’ve added a few more plants to it, but here is a more current photo:


Edited by MattyIce
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8 hours ago, Wisnasky-tank said:

So then do we think that colored lights like led do anything for growth or should it be strictly white/yellow lights that produce the proper growth?

See the @MattyIce post above. That is what you need. These are lights specifically design to produce growth in plants. White lights are designed to please us not necessarily the plants. And not only do the GE lights @MattyIce is using have the proper spectrum, they are very affordable!

A big thanks to @MattyIce for the graphic showing what they are, how they work, and the photo showing how they are being used and the results obtained!

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Compared the GE 32 watt, Phillipps 250 watt equiv , and kessil a360X tuna sun on my 150 shinning through a thick layer of duck weed and floating plants.  used manual settings on my camera except for the white balance so exposure settings are the same. 

GE 32 watt:

Phillipps 250 watt equiv:

Kessil a360X:

Since with the lenses they are similar to a single point light like the kessil or the sun, I get a little shimmer.  I just set up a tank with 2 of the GE's and 2 sponge filters for the water movement, here is a sample of the shimmer I get:


Edited by MattyIce
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