Randy’s Thoughts on Nutrient Target Ranges

[Superlightman]

I think it is a widespread misconception that plants, algae and corals "judge" light by intensity of photosynthesis or by a wide light spectrum. This is not the case.

Plants and algae use photoreceptor proteins with sensitivity in a +/- narrow bandwidth of the light spectrum. These photoreceptor proteins are cryptochromes and photochromes, both with maximum sensitivity in ca. 450 nm of the visible spectrum, and phytochrome with sensitivity in light red or dark red spectrum of light.

Blue light of 450 nm plays a major role in photoadaptation of algae and regulation of many other biochemical mechanisms of diverse organisms.

Blue light around 450 nm directly has the largest effect in daytime polyp contraction of corals (and here). It regulates circadian rhythms in most organisms and keeps them awake, that's why I don't recommend blue light for "moonlight". Real moonlight is in fact more yellow and red than sunlight. (See spectrum here. I have photographed under moonlight. It really is more yellow and red and less blue at "daylight" camera setting. The blue moonlight in movies and images is fake to imitate the human perception.)

Ironically it is exactly the blue light around 450 nm where LED lighting and T5 and metal halide lighting differ most.

In LED lighting, around 450 nm is the wavelength of royal blue LEDs and the activation light in white LEDs, causing a 450 nm peak of most white LEDs except some warm white LEDs.

In T5 and metal halides 450 nm is either the wavelength that is lacking from the beginning or it is the wavelenght that gets burned out and almost lost first.

Since 450 nm gets burned out first in T5 and metal halides, changing tubes or bulbs in lamps may cause major adaptation problems in corals which is known as light shock of corals.

Thanks that make sense, but if t5 were lacking 450.how can we explain their good results? T5 in my point of view after having testing most led on the market still outperform most of the led, how can we explain that?

 

[Hans-Werner]

Thanks that make sense, but if t5 were lacking 450.how can we explain their good results? T5 in my point of view after having testing most led on the market still outperform most of the led, how can we explain that?

1) I don't agree. After adaptation to LED lighting corals grow more beautiful and as least as good as under T5. A problem which may cause a delay in coral adaptation may be the 450 nm peak of LED.

2) To find out what makes the difference we would have to know the biochemical mechanisms of adaptation to the specific lamps.

 

[Hans-Werner]

Thanks that make sense, but if t5 were lacking 450.how can we explain their good results? T5 in my point of view after having testing most led on the market still outperform most of the led, how can we explain that?

... one mechanism could be connected to the fluorescence colours reefers like and want to make shine.

Red fluorescent corals like Montipora digitata and other Montipora species seem to be especially sensitive to increased blue light. This was already noticed by some reefers after T5 or metal halide bulb changes in the pre-LED era, althought not knowing the deeper cause, the increased blue light after the bulb change.

The fluorescent colors are provided by the coral host and without doubt they alter the light spectrum that gets to the zooxanthellae. More red light emitted by the fluorescent colors may cause such a maladaptation I am talking about above.

I also noticed problems with red fluorescent M. digitata, which are without problems under similar water conditions under T5 or metal halides, under LED. The color of these corals got an unsightly dull brown and they refused to grow under LED. High phosphate concentrations of 0.1 ppm or higher seems to overcome or at least alleviate the problems a lot and the corals got back their red colors and good growth. This is one of the backgrounds of my phosphate recommendations. However, other corals seem to do well with high phosphate concentrations too.

I also have red Acropora millepora which show excellent colors, shape and growth.

 

[Superlightman]

I understand your reasoning about the role of 450 nm and photoreceptor sensitivity, and I agree that blue light plays a major role in coral photoadaptation.
However, I’m not fully convinced that the issue with red Montipora under LED can be directly attributed to the 450 nm peak itself.
In my experience, I’ve never observed consistent problems with red Montipora under LED lighting, even at relatively low phosphate levels. Many modern LED systems produce excellent coloration and growth in red Montipora without requiring PO4 levels as high as 0.1 ppm.
It seems more likely that factors such as photon density distribution, light diffusion, overall spectrum balance, nutrient stability, and acclimation strategy play a significant role. A concentrated light source can behave very differently from a diffuse T5 field, even at similar PAR values.
Regarding phosphate, increasing PO4 may enhance zooxanthellae density and chlorophyll content, which could improve tolerance to high light stress, but that would be a physiological buffering effect rather than a correction of the spectral issue itself.
So while your hypothesis is interesting and biologically plausible in some contexts, I’m not sure it can be generalized to all LED systems or all red Montipora morphotypes

 

[Hans-Werner]

It seems more likely that factors such as photon density distribution, light diffusion, overall spectrum balance, nutrient stability, and acclimation strategy play a significant role. A concentrated light source can behave very differently from a diffuse T5 field, even at similar PAR values.

I have always used quite "diffuse" LED lighting, meaning always bars or arrangements of tiles, never concentrated LED beamers, since I am quite sure that beamers only have disadvantages. Since we usually don't imitate the almost 180° changing angle of sunlight I at least don't want a concentrated light source always at the same part of the coral with deep shadows in other parts. Diffuse light may not be the perfect substitute for a moving light source but at least acceptable.

Like stated above, higher sensitivity of red Montipora was already registered with "older" light sources.

Regarding phosphate, increasing PO4 may enhance zooxanthellae density and chlorophyll content, which could improve tolerance to high light stress, but that would be a physiological buffering effect rather than a correction of the spectral issue itself.

Phosphate alone in my experience does not enhance chlorophyll concentration in corals. I think it rather has effects in calcification and subsequent CO2 release from calcification.

Increased chlorophyll concentration in my experience is more related to higher available nitrogen, nickel and iron concentrations.

There may be other solutions to the problem besides higher phosphate concentrations, which would still need to be defined, like in so many problems in reefing.

 

[Ben0008]

My reef tank is 150g mixed reef, sps dominated, 4 years old. Skimmer, ozone, UVC.
10 ppm N
0,1 P
15 fish

My question or setup is, that I‘m now feeding the corals with ammonia bicarbonate of Randy’s receipt and add on top carbon (vinegar) to boost my bacteria.

Is this in combination a good idea to establish a stable system and feed my acropora and torches the best way?

 

[Randy Holmes-Farley Verified Community Expert]

Seems like a fine thing to do. I’d go with it for a while and see what benefit, if any, seems apparent.