Bay Area Reefers

I did a fair bit of research on spectral usage of various algae a while back.
Basically as part of a project with a few others on LEDs for algae turf scrubbers.

Key: Regular green algae is much better at using red wavelengths than coral.
So while adding some red to bring out the color is great, and yes, helps growth,
you are also unfortunately pushing the balance of power in the tank slightly toward the pest algae.

The reason is largely that most green algae is free floating, or near the surface, where coral is usually lower,
or at least has some floating green algae between it and the sun.
As such, the algae absorbs a fair bit of the red, thus, coral has adapted to use more of the blue.

Another note: It turns out the "Deep Red" is even better. Regular red is a bit short
for hitting the key Chlorophyll A peak. Few companies make Deep Red though.
LEDEngine seems to be the best.

It may be good tradeoff, since it will certainly help all growth. As long as you can keep pest algae in check.

I'd like to see your source for that as it does not ring true with what I have read on the subject nor my experience. Most green algeas are attached IME. That is, macro algae, not phytoplankon, since you were talking about ATS's

That also discounts the fact there is a LOT of coral growth in areas with no algae around, nor any between it and the water surface:

Yeah I'd like some sources too. Not cause I don't believe you but because I'm not exactly sure chlorophyll A is the only light converting pigment in corals or even the main one for that matter. I've read that chlorophyll c is another variety that is mainly found and the absorption spectrum for that is hard to find. Even if the red lights are only causing algae to grow faster they are at least helping the nutrient export so i'm not too worried. I feel like nutrient export outways spectral output of the lights with regard to pest algae. And nice pics Gresham.

I am a bit unsure on exactly what you are questioning, so I will add extra data.

Yes, I was researching macro-algae, but what I consider long term nuisance algae is usually macro algae.
Basically, hair and bubble algae being the most annoying and stubborn problems.
I deliberately grow hair algae in an ATS.

I do want to emphasize a very specific experiment I have been doing the last couple of weeks.
I replaced one of the old mostly-red LED modules with the new ones I am building for the main tank that are mostly blue.
This was to get a really feeling about how nuisance algae would do. Plus a few other things, but irrelevant here.
The algae under that light is definitely not growing as thick, and is browning a bit.
Does not prove anything about coral of course.

Some of it is just basic physics. I cannot remember the exact sources on algae absorption.
All I could find with a quick search was this. Mostly on general water red-absorption, but does mention and even
show how chlorophyll content changes water color.
ocean blue

I think you are really underestimating the amount of algae in the water, even apparently clear water.
But regardless, the water itself absorbs a ton of red.

Sure, lots of different corals do different things, as does algae. More of a general statement.

But I find it fairly amusing that two pictures you posted had RED coral.
If they are red, that means it is being reflected, not absorbed, and thus not used as much.
(Similar to Coraline algae BTW)

OK I will make it super clear....

This is what I am saying is not correct:

Your assumption there is a lot of free floating green MACRO-ALGEAE in and around tropical corals reefs does not ring true with what I have read, been told and have seen. There is not a lot of green free floating macro algae in the tropics. Not enough to inhibit coral growth. The real factor is depth when it comes to the more red light. There is very little phytoplankton as well around tropical coral reefs, one of the major factors in why you can get several hundred feet of vis on tropical reefs as opposed to around here in the MB where *IF* we get 30' it's a miracle.

FWIW I work with a Phycologist with multiple post docs... We're the worlds largest producer of marine phytoplankton concentrates so of course we have very knowledgeable people on staff. He concurs with what I have said. I am also a Dive Master, and have been for over 20 years. I do not need the "basics" taught to me, I've taught it to a few hundred classes over the years

Notice the large stand of GREEN staghorn?

I think your thinking of phytoplankton which has no relevance to macro-algae. YOu will not be growing much, if any, green phytoplankto with your ATS. There is also very little phyto in the tropics. Most lives in cold water.

I think I am being rather badly misquoted here.
Hence my confusion about what was wrong.
I never said anything about free floating MACRO algae.
Presumably that would be kelp, and yes, hardly common in the tropics.
Most algae is Phyto, and is green and free floating. I hope you don't disagree on that. But yes, very unclear.

---

I will take your word for it about the water absorbing far more red than the algae. Especially in tropics.
I quite readily admit I do not know the absorption percentage difference between them.
But also note this from my comment:
> But regardless, the water itself absorbs a ton of red.

-----

Anyway, I don't want to start a flame war.

But do you think this is wrong:
* Most corals are adapted to using more of the blue end of the spectrum, while algae are adapted to use more of the red end.
A much more important comment.

Yes, not even close to the only pigment
See enclosed.

Now I totally agree on nutrient export being worth it. The whole point of an ATS.
But I do want to emphasize that algae only helps nutrient export if you then manually remove it.
If crabs/etc eat it, nutrients stay there.

Hey, I found the source I liked.
In particular to the arguments above, look at chapter 9, page 117.

Book on photosynth

So I read a bit of that and I think the argument is justified in some ways. It said that the deeper the coral is in the water column the more of that blue/green absorbing pigment there is. Thats not to say that all coral in our tanks are found in deep water. And I don't want to say this so prematurely but I might as well, the corals that would likely be in shallower water are taking to the red light a lot better than those that aren't found in that region. Ultimately though the sun puts out so much broad spectrum light that pest algae would be fine growing among reefs, the only reason they aren't is the nutrient levels and CUC in my opinion, which is from an amateur biologist