Why Too Much Light Can Be Harmful to Zooxanthellae

[A. grandis]

I agree that constant food availability is one of the biggest differences between our tanks and the ocean, and suspect it matters. Nutritional status definitely affects stress tolerance and thats a big difference in nutrition -- feeding constantly in the ocean vs feeding almost never in aquariums.

With that said, most animals in nature experience environmental stress in their normal habitats. I have no reason to think the corals in nature are not stressed by high light. In fact that's one of the theories for the evolution of fluorescent proteins in corals, for use as sunscreen. The simplest explanation seems to be that they are stressed by the high light levels but have adapted to deal with it.

It seems like an important distinction in my mind, because it suggests there may not be a good reason to blast corals with high light in an effort to mimic nature, even recently imported wild acros. (Which is probably good, since none of us are hitting the 1000 PAR I've measured on some shallow Australian reefs :) )

The normal/ example of how it should be is the ocean. To mimic nature is to offer the very best to the system, within our limits. We can offer strong light, but we hardly can feed in a closed system like in nature. The confined space has automatically way more organics and nutrients comparing to nature though. That's why we can offer higher light intensity and be very successful. Quality light includes real UV and IR with a relatively uniform distribution and stability, with water temperature control.