Reef Myth, Red+Blue LEDS vs White LEDS?

[Erasmus Crowley]

Hi guys.

I just had a conversation here on the forums about LEDs for macroalgae refugiums and I realized that there is a widespread idea that might actually be purely myth. I tagged your BRS account in that thread, but I wasn't sure if you'll actually see it or not. My apologies if this ends up being duplicated effort, but I think that it would be awesome if you guys decided to run some experiments and settle the issue.

It seems to me that nearly everyone in the saltwater hobby believes that red+blue LED grow lights are better than white LEDs when it comes to growing macroalgae such as chaetomorpha. However, I've spent a decent amount of time on YouTube, and I tend to watch a lot of videos about various other hobbies. One of those hobbies that I enjoy learning about happens to be indoor gardening. In that hobby, there have been quite a few YouTubers that have tried to tackle the red+blue vs white LED debate.

Long story short, every single video that I've been able to find on the topic (regarding terrestrial plants) has come to the conclusion that when grow light LEDs are matched to the same watt consumption, white LEDs result in more growth as measured by weight, and stronger plants. The red+blue LEDs will result in leaves that are smaller and/or more malformed, and the plant ultimately has weaker, thinner stems which eventually fail to support the weight of the plant. I've never been able to find a single video where white LEDs and red+blue LEDs are put head to head and the result is that the red+blue come out on top. The spectrums of light that are omitted from the red/blue LED bulbs seem to have some unknown effect that results in better growth than you get by focusing purely on maximizing photosynthesis.

I've seen Ryan say some variation of "Red and Blue are the main spectrums of light required for photosynthesis" in MANY of his videos, usual as praise for the energy efficiency of growing algae with a light that is primarily red+blue. However, given what I've described above, there might be good reasons to reconsider that line of reasoning.

Having said all that, no one has ever (that I'm aware of) actually tried tests like this focused on marine macroalgae. Chaetomorpha doesn't have leaves or stems, so it would be impossible to tell if they are malformed, but it seems like it would be easy to see which bulb type results in the greater weight gain over a given period of time with an equal power consumption between them.

If you read all of that, thank you! I hope this arouses your curiosity as much as it does mine.

 

[davidcalgary29]

I'm interested in this topic myself. I've read a few scientific (translation: usually dry and inaccessible to the layperson, and even to those who have an interest in the topic) papers, but few of them address specific lighting requirements for optimal growth in the home aquarium. I'd love to see a careful study taking into account algal types, lighting methods, nutrient levels, livestock(ing), and water volumes. I have macro in three jarquariums and, as I'm finding out, light distribution in pico volumes of water encased by glass in circular containers is vastly different from a single fixture suspended over a rectangular nano tank.

 

[blasterman]

In terrestrial plants red light causes internodal stem growth. It's basically a photo trigger that a plant is growing in a competitive environment. Blue light causes vegetative growth - fat and bushy because it tells the plant nothing is growing close. Ive tested this with house plants.

Marine algae can use both blue or red light for energy. A cool white LED is basically a blue LED with a smidge of green and red.

Orange/or red LEDs do not deliver as much energy as blue or white LEDs. This is a fundamental physics issue. In a white LED some of the blue energy gets converted to green and orange/red, but most of the blue energy is still there.

Red light doesn't grow algae any better than blue. This is one of the most absurd myths 8n this industry. If anything you will get better efficiency with white or blue because of physics. However, there's a lot of money to be made selling R/B kessils and other gimmicks. A cheap cool white shop light does just as good a job and costs like 1/10 per unit of PAR. The guy buying the boutique over priced R/B light isn't going to admit he's wrong though.

BRS was supposed to be doing a test on this, but I would be amazed if we see it. Why would they undermine their own products? The one guy still claims halides dont grow coral well because halides don't emit much violet and he can't admit that myth as well.