Any benefit to lower PAR levels?

[LordJoshaeus]

Hi everyone! Here's another question...in my research on freshwater planted tanks, I found that lower light planted tanks are often significantly easier to manage than brighter planted tanks - the lower light slows algae growth, and as it also slows the growth of the plants they do not need to be trimmed as often (which is required to maintain good circulation and avoid excessive shading of the lower foliage) and do not go through nutrients as quickly (freshwater algae problems are frequently caused by one or more nutrients falling too low to support healthy plant growth). My question is, are any similarly positive effects observable with coral and/or macroalgae tanks? I was thinking of trying a tank with 50-100 PAR...any photosynthetic corals would be fed twice a week to partially offset slower photosynthesis rates. Thanks

 

[PotomacReef]

Algae growth is based on spectrum as well as intensity. In planted tanks you have a lot of bright white lights, which grow both algae and plants really well.

For reef aquariums, we have the advantage of being able to turn down red and white lights to maximize the coral growth to algae growth ratio.

I think that's the main reason why people in the reefing hobby run high PAR levels -- they can just keep it very blue! That gives good coral growth and low algae growth.

 

[LordJoshaeus]

Algae growth is based on spectrum as well as intensity. In planted tanks you have a lot of bright white lights, which grow both algae and plants really well.

For reef aquariums, we have the advantage of being able to turn down red and white lights to maximize the coral growth to algae growth ratio.

I think that's the main reason why people in the reefing hobby run high PAR levels -- they can just keep it very blue! That gives good coral growth and low algae growth.

That's odd...when I researched planted aquariums, I didn't find any strong correlation between red spectrum and algae growth. When I had my 10 gallon, it also was quite blue (half the LED diodes were actinic and the other half 10000K) and still had major algae problems. Except for corals and macroalgae that grow so deep that red light is all filtered out by the seawater, I can't envision a lot of reason why ornamental macroalgae and corals would prefer strongly blue light while pest algae would grow on either...surely most macroalgae and zooanxthellae have chlorophyll as a pigment for photosynthesis?

 

[PotomacReef]

Lighting for Algae Cultures

About light and photosynthesis When we talk about light for photosynthesis, we are talking about PAR (Photosynthetically Active Radiation). This radiation consists of photons of light that are between 400-700nM in wavelength. (Explore the ARS Algae Lights) To choose the correct light for...

algaeresearchsupply.com

Check out that link, then look at the planted tank v reef tank lighting spectrums below:



This is the spectrum of the Kessil Tuna Sun...look at the full spectrums (6k-9k)...you can buy similar spectrum bulbs at a hardware store as "daylight" lights. These are optimized for photosynthetic plants and algae.

This is the spectrum for the actinic ATI bulb for growing coral:

Much less green and yellow, almost no reds and it's considered much bluer than even 10k. The ATI Coral plus, for example, has a red spike.

 

[LordJoshaeus]

The problem is that the zooxanthellae in corals also use red light - they contain Chlorophyll a and c, both of which primarily absorb both red and blue light. (Side note...as dinoflagellates, they also use Peridinin and cartenoids and can thus absorb blue/green light in the 470-550nm range. It's amazing what you learn when you do spontaneous research such as this). I don't understand why increasing blue light and decreasing red light would hinder pest algae growth without doing the same to corals and many macroalgae.