Please explain over-production of zooxanthellae if zooxanthellae is expelled from the coral if the zooxanthellae is responsible for oxygen toxicity in corals in high intensity light conditions?
The expulsion of the majority of zooxanthellae from a coral is what allows us to see the underlying colors in a coral. Under high lighting such as metal halides create a recession and a depression in the zooxanthellae concentration in the tissue to prevent O2 toxicity... Zooxanthellae is responsible for photosynthesis, however, an excess of zooxanthellae is what you tend to see as darkening or browning of the coral to increase the nutrient uptake, especially with frags and distressed coral colonies not receiving sufficient light.
The article is correct about the trace elements and minerals being removed via protein skimming and other mechanical filtration methods, however, the corallary to the fact that Potassium only promotes reds is false.
Potassium supplement to the salt water aquaria promotes BLUEs and PURPLES.
Iron, which is amply found in ocean water, promotes green (photo-inhibition measures)
Iodine promotes Reds, Oranges, AND Pinks.
Photo spectrum from lighting does not solely increase color of corals... intensity does...
Good growth lighting for corals do not promote good coloration per se... nor does the flipside of that statement where good color rendition of corals, to the human eye, is the best for coral growth and health.
I have seen aquariums with good lighting and bad water chemistry fail... I have seen good water chemistry and not so good lighting succeed... yes... the corals are stretched out and brown... but mass growth had increased exponentially... what you need is both to be adequate... the right spectrum for coral growth... the right spectrum for photo-inhibition... good water chemistry... and last but not least, STABILITY
Cheers!
