Keeping SPS, LPS or Soft Corals in a Saltwater Aquarium
In our experience corals can not simply survive alone off light; a lot of people make the claim that they can. We have often wondered if they can survive off of light why do they have a Gastrovascular Cavity, also known as a stomach. They also have a mouth for food intake and tentacles to gather food. So, corals can not survive off of light alone - they also need a good source of plankton.
All Corals have muscle fibers just like humans do, these muscle fibers are also known as Epitheliomuscular cells. These cells are located within the epidermis of the coral. Without these cells the polyps of the coral would not be able to expand or contract. When we first started studying corals we realized how amazing the creatures actually are. These muscle fibers also help the coral open and close due to changes in light, to capture food, and even protect themselves from predators. Just like with people, these little muscles the corals have require a great deal of energy.
Another way that the majority of corals can acquire the fuel to function is through their symbiotic zooxanthellae. Zooxanthellae is a type of symbiotic algae that resides within the corals gastrodermis (or tissue). Corals open wide to father the light for Zooxanthellae and in return the Zooxanthellae provide the coral with several alternative food sources such glucose, glycerol and amino acids. The Zooxanthellae are also responsible for the coloration of the corals. If the Zooxanthellae should not get what they require from a light source or the coral, they will begin to lose their pigment and turn white; a process known as "bleaching". Bleaching is just how it sounds. The coral slowly loses its color until it has turned white.
Another reason to make sure you are supplementing your corals food source is to help protect the Zooxanthellae. Zooxanthellae require more than just light to survive; they also require nitrogen and phosphate. If you are feeding your corals they can produce these two nutrients themselves to directly support the health of their symbiotic algae. This is exactly what a symbiotic relationship is. The coral feeds the Zooxanthellae by consuming plankton and then the Zooxanthellae in return feeds the coral.
Coral lighting requirements...
The next topic we want to address is light, this usually becomes a concern of ours. In our opinion NO CORALS should be kept under T5 lighting, anything less than strong LEDs or Metal Halides should not be attempted. Just because a coral might be able to survive under T5 lighting doesn't mean it should. If you are someone thinking of establishing a full blown reef tank, don't blow a ridiculous amount of money or corals and then bleach them out with lights that most likely incapable of keeping light intensive corals alive. And every single one of them is a light intensive coral - SPS, LPS, and Soft Corals. It's because they are corals and they are genetically predisposed to survive off of sunlight. Before a person should shop for any corals, we recommend first splurging on lights. Everyone here at the store will only run Ecotech Marine Radion lights at nearly 80% intensity.
Where to place your corals...
Irrelevant. We have seen corals that should be almost sticking out of the water prefer near the substrate and then ones that should be on the substrate sticking out of the water. Generally speaking though, SPS corals do prefer to be higher up in the tank, LPS corals prefer the middle of the tank, and soft corals prefer closer to the bottom. When you purchase a new coral it's usually best to acclimate them by starting them out lower in the tank and gradually move them over the course of a week or two. This way you can see if they are adjusting well to any changes by paying attention to polyps extension and the color of their tissue. If a coral is getting darker it means it's trying to absorb more light. if it's getting lighter it means it's shedding Zooxanthellae in an attempt to adjust to excessive light.
All of this is just our experience with corals and general guidelines that we have seen work. Should you have any further questions don't hesitate to reach out to us on our Contact Us page.