LIVE SAND

Live sand varies in its composition depending on where it was collected, but it typically consists of coral sand (i.e., pulverized and eroded pieces of coral), pieces of the calcareous algae Halimeda and the remains of minute, shelled protozoans known as forams (Order Foraminiferida).

Some of the sand around coral reefs is the result of the feeding activity of parrotfishes. These fish rasp the coral surfaces with their hard beaks to get at boring algae and then crush the calcareous material into fine particles with their specialized pharynx. The parrotfish excrete this indigestible debris in big clouds and the resulting material ends up on the sea floor.

The live component of the sand includes aerobic and anaerobic bacteria, forams, annelid worms, crustaceans (primarily isopods and amphipods) and, occasionally, tiny brittle stars. The grain size varies from very fine to chunky. I prefer a medium grade in which the grains are about the same size or slightly larger than a pinhead. I have found that the very fine grades may remain suspended because of water pumps, which can result in clogged external filters and destroyed impellers. On the other hand, large grades are more difficult for our clean-up crew to keep stirred up .

I would suggest placing about 2-3 inch of live sand on the bottom of the aquarium. Then place the live rock right on the sand. If your reef aquarium is already well established, make sure you get the sand behind and around the reef structure when you add it.

The advantages of including live sand in the reef aquarium are many. First of all, it looks better than a bare, glass bottom and egg crate! It also provides refuge for those fish that bury in the substrate and invertebrates that hide and reproduce in the sand. In turn, these invertebrates can provide an important food source for fish that feed on animals that live under the substrate.

The light color of the sand reflects light off the aquarium bottom and makes the tank look brighter. This reflected light will benefit those zooxanthellae-bearing invertebrates near the bottom of the aquarium.

Most importantly, the bacteria-laden sand will help reduce ammonia to nitrite and nitrite to nitrate, and anaerobic bacteria in the sand will break this down into nitrous oxide, which will diffuse from the aquarium. The sand is a natural denitrifier in that it will help to control the buildup of nitrate in your aquarium. Its been seen nitrate levels drop by half in as a little as two days after live sand was added. It is also a great way to inoculate a new aquarium with nitrifying bacteria. And, if that were not enough, live sand will also help maintain your pH and alkalinity levels!

As far as detritus that collects among the sand particles is concerned, much of it will be broken down by the wealth of heterotrophic bacteria that live on the sand grains. But, it is also important to keep fish and invertebrates that continually turn over the sand surface. The fish that are best equipped for this task feed from or bury in the sand.