It is my understanding that nutrients in the water can also effect coloration. Higher nutrient levels support higher concentrations of zooxanthellae algae in coral tissue...this is usually yellow to brown in coloration. Excessive nutrients can dull the colors...but if you have a nutrient rich system, many times your zoanthids will have a richer/deeper coloration.
Whereas a system that is lower nutrients will have tend to have the brighter, neon type colors. While those look cool...it is easy to take it a little too far to the point where the polyps start looking a little bleached.
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