[Serioussnaps]

Originally posted by elegance coral
I think you pretty much got it. From what I have seen and studied this is how I believe this works. There are different clads of zooxanthellae (algae). These different clads are better suited to different environments. In order for an Elegance coral to survive at greater depths they need to utilize a different clad of algae than the shallow water corals. This clad of algae is not well suited for a bright light environment. They quickly begin producing an excess amount of O2 under bright lights which causes severe damage to the coral. The shallow water corals are utilizing a different clad of algae. This clad has a much wider range of acceptable light than the clad of deep water corals. There is still a minimum and maximum light requirement for these shallow water algae. This is why I doubt that a shallow water coral will do well in your sump. In my tank I have 7 deep water corals and 1 shallow water coral. I have the lights set as strong, and on for as long, as I can without causing my deep water corals to swell up. I have the shallow water coral at the top of the tank where it is getting more light than any of the other corals. It has been in the tank for about 2 weeks and has gone from being almost transparent to a dark brown color. It was not showing signs of bleaching. It was just a healthy shallow water coral. My deep water corals have faded in color as I force them to adjust to brighter lights. I believe they are at there limit. The tentacles of the deep water corals that are more exposed to the light are almost transparent while the shaded tentacles of the same coral are a brown color. So these two corals of the same species in the same tank are acting differently to the same set of lights. The shallow water coral is showing signs of adapting to a dimmer environment while the deep water corals are showing signs of adapting to a brighter environment. Even though the shallow water coral is higher in the tank. I'm not sure how well the shallow water coral will do in this tank in the long term. I may have to move it to a brighter tank. I really would like to leave it in the tank with my deep water corals. Hypothetically, as the shallow water coral regulates the population of algae within its tissues, it could discharge small amounts of it's clad of algae into the water. Hypothetically again, the deep water corals if very close to their maximum light level could retain this shallow water algae. Hypothetically yet again, over time the deep water corals could become shallow water corals. Still hypothetically speaking, the opposite could take place where the shallow water coral could retain the clad from the deep water coral and I would end up with all deep water corals. This would hypothetically stink.
Did any of that make sense?

Makes plenty of sense.