LED Color Distribution for Planted Tanks

[dsm7]

Hey everyone,

Quick question on LED color distribution for planted tank lighting.

I've seen each of the following statements made online, many of which contradict one another:

• Red lights should take up at least 50% of your LED spectrum, while blue lights should not exceed 15% (with the rest, of course, being white).
• You don't want to overdo it with red lights, since having them on for a prolonged period of time will result in excessive algae growth.
• Red lights are useful to the plants that they reach in shallow tanks; however, as blue light permeates further, blue lights should be optimized when lighting a deeper tank.
• Shoot for 75% of your spectrum being composed by blue lights, 20% by white lights, and just 5% by red lights.
• It doesn't really matter, as long as you don't overdo it with the blue lights.

Despite the internet being information-rich for most niches of the aquarium hobby's world, there seems to be limited discussion on this and even less consensus.

Does anyone have input on the matter?

Thank you!

 

[Colin_T]

The amount of red and blue light that penetrates aquarium water is usually 100%. This is because aquariums are shallow and light doesn't get reduced very much, if at all in really shallow water (less than 6 feet).

If you want to grow plants, have equal parts red and blue light, and throw in some green. Then add some white to brighten it all up.

 

[davros]

This is a topic of interest for me. I agree many conflicting opinions.
I think some of the early science will conflict at bit with later publications.
Sometimes they seem (to me) to only focus on one aspect of the plant and ignore others.
Vendors seem to latch onto something to push. Lotsa "pink' and "royal blue" getting mentioned...

I did try just blue and red and the plants and fish looked weird.

Current plan is to have roughly equal "wattage" of red , blue, green and
wider spectrum white and PWM the 4 channels till I like the look and and things grow

 

[StevenF]

• Red lights should take up at least 50% of your LED spectrum, while blue lights should not exceed 15% (with the rest, of course, being white).
• Shoot for 75% of your spectrum being composed by blue lights, 20% by white lights, and just 5% by red lights.
• It doesn't really matter, as long as you don't overdo it with the blue lights.

Most of the numbers in this refer to the number of LEDs but NOT the output power of them. You can buy one very bright LED or one Very dim LED and the actual chip in each is about the same size. The actual chip that produces the light is a little smaller than the head of pin. Most of what you see is a heat sink and protective packaging. IT is the amount of light produced that matters. Not the number of LED chips.

Also while blue and red light are the easiest colors of light plants can absorb plant actually can make use of the entire spectrum of light.dditionally the vast majority of white LEDs on the market produce bed and blue light. And depending on the plant species you may not get good growth with red and blue lights only. So you really want more white. Some plants may grow much taller than normal if they don't get enough red.

• You don't want to overdo it with red lights, since having them on for a prolonged period of time will result in excessive algae growth.
• Red lights are useful to the plants that they reach in shallow tanks; however, as blue light permeates further, blue lights should be optimized when lighting a deeper tank.

This is mainly speculation. There is no scientific studies to prove it. What has been proven is that other than light CO2 and water plants need 14 elements (nutrients) dissolved in the water to grow. And if just one of these elements is not present plants will now grow. And yet algae will grow every well in these same conditions.

Most tanks that have algae issues have Nutrients issues and not a lighting issue. IF you have a nutrient issue dimming the light can sometimes help. This works by slowing down plant growth allowing the production of nutrients from fish waist and food so the production of nutrients keeps up with the need of the plants.

And using a fertilizer is no guarantee that you will have all 14 nutrients. In fact Most fertilizer don't have all 14 nutrients in them because the manufactures are counting on your water to provide some nutrients. But not everyone has the same water and some people must use RO water which essentially has no nutrients in it.

 

[StevenF]

Despite the internet being information-rich for most niches of the aquarium hobby's world, there seems to be limited discussion on this and even less consensus.

The big issue in this hobby few people do science experiments to to confirm what they have experienced. Most recomendations you read are from a persons experience. On this forum you will find little on lights since most tanks here are low tech. But if you go to forum were that focuses on high tech aquarium, Estimative Index, or hydroponics you will find a lot more.

The key thing you want in any aquarium light is a dimmer. That way you can use a light the is brighter than you need but dim it down to a light level that works best for your tank. It also should be on a timer so that it will turn on and off automatically. The fish will be most comfortable in a tank with a predicable day night schedule.

When I built my aquarium light I used high power 12VDC while LED light strips with a CRI (Color Rendering index) of 90+ and color temperature of 3500K. I then later added some low power 660nm Red lED light strips because my plants were growing to double or triple the norm height. Link to the white LED I used. I cannot find the web site for the red strips I used.

90% of the light comes from the white LEDs which on maximum power will put out 3000 lumens of light. That is a lot of light for a small 5 gallon tank but it is still only about 1/8 of the light produced by the sun on a clear summer day. I make it this bright so that I could try high tech if I wanted to but most of the time it is dimmed down to 30% to 50%. If I wanted to I could run it at only 5%. The tank doesn't get any direct sunlight and the room doesn't get a lot of sunlight anyway.

CRI is a indirect measure of the spectrum of light produced. 90 means it is producing about 90% of the visible colors of light produced by the sun on a clear day. 3500K is the overall color of the light. less than 3000 the light looks a little yellow. Above 4000 it gets a little bluish. 3500 is what I prefer.

These strips do produce a lot of heat. So I mounted them on a sheet of aluminum. The sheet has about 4 times the surface area of the steps in contact with air. This keeps them cool enough that I don't need a fan. I then attached a clear it to a clear sheet of acrylic (1/3 inch thick) that is cut to the same size and shape as the original plastic lid that came with this aquarium.