Aquarium Fish

Coral Reef Zones

Ah, the coral reef. The beautiful coral reefs of the world are often the primary motivators for people getting into the saltwater aquarium hobby. So, let's talk more about coral reef zones and start with some of the different areas of the coral reef. When researching the corals you're interested in keeping in your home reef tank you'll often come across various terms explaining coral reef zones. There are several to know about for our purposes. We don't cover all the zones here, just the ones where most of the corals we're keeping are found most often on the reef.

Knowing which part of the reef your coral comes from can give you some insight into some of the captive care requirements, or helpful hints if you will, of what you need to do to get a particular coral to grow and thrive in the home aquarium. As always, please research all corals before you buy them for your reef tank setup to determine if you can adequately provide for them.

Coral Reef Zones
Photo courtesy of the U.S. Geological Survey

Let's talk about some of these reef terms.

Coral Reef Types

  • Fringing Coral Reef - these are coral reefs that form along side the shore or coast line. These reefs often have high flow rates and often intense sun light due to the shallower water depths.

  • Patch Coral Reef - this is a small coral reef often isolated from other reefs. They can form as a result of a sunken ship or they could even be what is left of an older reef structure.

  • Barrier Coral Reef - this type of coral reef is one that runs parallel to the coastline with a lagoon between it and the shore. Think of the Great Barrier Reef.

  • Atoll - is a coral reef that forms a circular or mostly circular shape and encloses a lagoon. These can form around submerged volcanos or small islands that have fallen below sea level.
Coral Reef Zones
  • Inner Coral Reef or Reef Flat - sometimes used when referring to the shore side part of a coral reef. The water is sometimes quite shallow with some corals even being exposed to the air with the changing of the tides. Water motion is usually lower than the reef crest or outer reef. Nutrients can be high here due to land based run offs.

  • Coral Reef Crest - the area where corals experience high water energy/flow from breaking waves. Corals found here are used to high light levels too.

  • Outer Coral Reef or Fore Reef Slope - this is the side of the coral reef facing the ocean and it is the wall that rises from the depths. This part of the reef also has very high water flows and towards the top of the coral reef slope, high light intensity. Corals lower on this reef wall often lack zooxantellae which means they get most of their nutrients from the water rising from the oceans depths or the corals above them.

  • Lagoon - a lagoon can form between land and the coral reef. These are associated with Barrier Reefs and Atolls. Some can be quite calm and water temps can climb higher here too.

Armed with this information we can sort of figure out what type of conditions may be helpful to replicate in our reef tank for the corals we keep. Now, go research those corals!

Author : Mike FishLore

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