OP
OP
Thanks for pointing this one out, since I haven't done an update on this in 7 years, this is another item that falls under the axe. I as well have been running my scrubber on my personal tank 24/7 100% for a few years with no issues. Randy Holmes-Farley posted somewhere at one point that he also didn't see any negative effect in 24/7 lighting for macro (I don't believe his comment was specific for an algae scrubber).
I will throw in this: if someone thinks that saturation has something to do with duration, IMO, they're wrong. Saturation has to do with instantaneous conditions.
In the instance of photosaturation or photoinhibition, this very much has to do with intensity and nutrient availability. This issue is more prominent with LEDs due to the focused spectrum, which is generally focuses on those parts of the spectrum which cause hyper-excitation of chlorophyll (the infamous A and B peaks). So what happens is that if you have the intensity (not the duration) very high, and your nutrients are very low (or you are not delivering the nutrients fast enough) then there is an instantaneous imbalance of light-energy (excess photons) compared to the nutrients, and the algae can't do anything with that excess energy. To a certain extent, you can mitigate this with on/off cycles so there does appear to be some ability to process under excess light conditions, but I think that also depends on how much excess there is. I think there are certainly conditions where photosaturation is so extreme that nothing will grow.
The examples where the center of a screen is bare white and the extremities are full of GHA growth are prime examples of the photosaturation effect in action.
Running 24/7: yes, you can do it. In fact, if you can dim the lighting, this is the best way to operate, IMO. Find the "sweet spot" where your instantaneous intensity works with your level of nutrients, and as long as you keep feeding the fish/corals on a regular basis, you can balance the scrubber "input" (dirty tank water) with the tank "output" (waste) and run that level of illumination 24/7. It's not just for high-nutrient tanks, that would be my only add-on
It's entirely possible that running a scrubber 24/7 might actually create an environment that excludes certain types of macro algae growth. This is interesting because I hadn't really considered that before. I get pretty consistent growth on my unit that runs 24/7, both in type and volume.
I'm not sure where you heard that, but if you google Otto Wartburg (warburg?) and "flashing" you'll see a study he did about 80 years ago where he determined that you can flicker the light source on and off, creating "dark" period that is 10x longer than the "light" period, and get the same photosynthetic output from chlorophyll compared to constant light. That's at something like a 1 kHz rate, and may not be a direct comparision, but the "dark" part or the cycle does require no light, AFAIK. Think of it like a 2-bucket system. Bucket 1 gets filled by photosynthesis. Bucket 1 empties into Bucket 2, which leads to a different process, but the actual emptying of Bucket 1 into Bucket 2 is the "dark cycle". So if Bucket 1 is always getting filled, that cycle doesn't work to maximum efficiency (but it still works).
Flashing studies have also been done on coral tide pools in Hawaii. So when you're in the ocean or in a pool and see those dancing lines of intensity on the floor when it's sunny - that's effectively the same as flashing, and it has a huge effect on all types of photosynthesis. I'm of the opinion that no matter what light source you're using for a scrubber, you're already doing this and you don't even know it. Like that Palmolive commercial. But I digress. The effect of the falling water acts like waves in a pool, to some extent. If you dim LEDs with PWM dimming, this might add to the effect. But there's no proof behind that, or else I would have made a big deal out of the fact that I use PWM dimming.
To some extent, maybe. I'm not a biologist either but I did sleep at a Holiday Inn Express at some point in my life.
Here's how I understand it. Chlorophyll A is used primarily, this is the far red (660) and the hyper-violet (400-420 ish) spectra. These are "readily available" on a cloudless sunny day. But these wavelengths don't penetrate clouds or deep water very well, and they also don't penetrate atmosphere at an angle very well (i.e. sunrise/early morning and sunset/early evening) so nature has adapted the ability to use Chlorophyll B spectra under these conditions and maximize sunlight-harvesting ability under poor and/or imperfect conditions - the 630 and 440-460 spectra will penetrate clouds and water better. So A and B are just 2 ways of achieving the exact same goal. Of course, you can use Red A and Blue B and get results, probably because there isn't a switch where the cell says "ok folks, A is available so were dumping B from the process"...it uses whatever it can to survive and thrive.
Circling back to the photosaturation discussion, B more easily can cause photosaturation in our scrubbers, and this might have to do with it being artificial. This falls under the same umbrella as early-adopters of LED for displays learned - the Cool White/Royal Blue issue, where people would adjust the lighting so that everything "looked" the way it used to under halides or T5HOs, and they would smoke all their corals. That's photosaturation (of the zooanthelle).
What I'm getting at is that when you run a 630 and a 660 at the same current, the 630 will output 3 to 4 times the radiometric flux (photons). The photosaturation is almost guaranteed. In my experiments (and others) and customer feedback, the same is the case with RBs vs HVs. The Royal Blues will saturate right in front of the LED. This rarely happens with Hyper-violets.
As far as what red does and what blue/violet does, red seems primary and blue/violet seems to "enhance" growth. Again I can't claim biologist here but I call it as I see it - algae grows better with a very slight blue/violet addition into the light mix, and it does so much better with violet vs blue. Again, violet is in the A and blue is in the B, so Red A and Violet A...maybe it's nature anticipating that those two will "be coming in" together, and a man-made Red A + Blue B "works"...but it's really hamstringing the system.
