What Live Sand Is and How It Is Used in a Saltwater Aquarium

Saltwater Aquarium
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Live sand, or LS, is natural reef coral sand that is collected live from the ocean, or non-living coral sand that is cultured to make it live. What makes it live is the microscopic biological bacteria that grows on it, and the many tiny crustaceans and other micro and macro-organisms that reside in it. Live sand can serve as the main base for biological filtration in a saltwater aquarium, while the organisms help consume organic matter in the sand bed.

Some of the organisms provide a natural food source for many aquarium inhabitants as well.

What Type of Live Sand to Use

There are many types of sand (live or nonliving) to choose from, but the best is sand made from coral, such as coral sand, reef sand, crushed coral or aragonite. One top choice of many expert aquarists is Aragonite by CaribSea. Some sand sources other than aragonite types may have silicates in them, which you do not want in your aquarium. Silicates cause algae problems, and once introduced are next to impossible to remove.

Pure LS vs. Seeding

There are three basic approaches for starting an aquarium with live sand:

  • Use 100% LS, which can be very costly.
  • Use a 50/50 combination of LS (new store-bought sand or used sand from an established aquarium) and non-living sand. By mixing the two together (called seeding) you save money, and the LS converts the non-living portion of the sand into LS over a shortened period of time, as the biological bacteria and living organisms multiply and populate the non-living sand.
  • Use nothing but non-living sand. All sand eventually becomes live over time, due to the nitrogen cycling process. However, starting from scratch requires much more time to develop live sand.

If you have a new aquarium in the initial stages of the nitrogen cycling process or one that's still in the process of completing its cycle, you can use the seeding method to kick-start or speed up of this transition.

For an aquarium that has been running for some time, seeding can also enhance the strength of its existing biological filter base.

How Much LS to Use

Unless you are going to be using the Jaubert/Plenum method of filtration, you should avoid excessive amounts of live sand. The sand bed becomes too thick, which allows unwanted DOCs (dissolved organic compounds) to get trapped, contributing to the growth of undesirable micro- and macro-algae. Here are some suggested amounts of live sand to use from noted experts:

  • In his book Simplified Reefkeeping, author Robert Metelsky recommends a thickness of approximately 1 3/4 to 2 inches, which calculates to 1.45 pounds of sand per gallon, or 80 pounds for a 55-gallon tank.
  • In The New Marine Aquarium, author Michael Paletta's recommends a depth of 1/2 to 1 inch.

As you can see, there is some variation among the recommended amounts, and, indeed, different tanks will need different amounts. But the bottom line is that a layer between 1/2 inch and 2 inches covering the bottom of the tank should be sufficient. 

Purchasing Live Sand 

How can you be sure you're getting live sand or dead sand?

This is a good question. With live rock (LR), you can see that it is live, but not so with LS. The best way to ensure good-quality live sand is to purchase it from a reputable supplier that collects it directly from the ocean or specializes in cultured LS and offers fast shipping; the shorter transit time the better! You can also buy LS from an established local fish store, but this might be costly.

Just like with LR, some die-off will take place during shipping, and the live sand will most likely go through a cycling process of some kind. How much cycling is necessary depends on the viability of the LS when it was shipped and how much die-off takes place during transit.

Adding LS to the Aquarium

If you are using live rock in the aquarium, it's best to elevate the rocks off the bare bottom of the tank.

Many marine animals burrow into the sand. As they do so, any rocks that sit on top of the sand will slowly get lower and lower in the substrate as it gets displaced. Allowing the sand to be placed "under" the rocks prevents them from getting buried deeper in the sand, eventually ending up sitting on the bare bottom of the tank. It also prevents the rocks from being dislodged, and it prevents stacked rockscapes from becoming unstable.

Once you are done aqua-scaping and elevating the LR, or any other large sized decorative non-living corals or rocks, it's time to add the substrate. Add the LS slowly to prevent excessive clouding of the water. If you are using live rocks in the tank, do not pour the sand onto the rocks, as this will smother the LR and cause oxygen depletion.  

LS Substrate Maintenance

The aquarium should include inhabitants that will stir or turn over the live sand. These animals are referred to as sand stirrers (or sifters) or tank/reef janitors, custodians or cleaners. Recommended types of detritivores include hermit crabs, shrimp, crab, sea urchins, sea cucumbers, and starfish, For sand-sifting fish, try gobies, mandarinfish or jawfish. 

Before adding janitors of any kind, it's important to learn about them first. Do your research on animal compatibility and dietary requirements (especially when it comes to the fish named). Also make sure that the animals you choose are not toxic, like some cucumbers are, or otherwise hazardous to other tank inhabitants. With the right mix and quantity of reef janitors, a live sand bed should not need to be deep siphon cleaned. Of course, it's still important to follow good a maintenance routine, and you should siphon any uneaten foods or excess debris from the "surface" of the sand bed and between rocks whenever needed. 

In general, working with live sand is similar to working with live rock. Test the water parameters to monitor what is happening in the aquarium. Add new occupants slowly (one or two at a time) and only when the tank has completely settled through the cycling process or any recycling that may occur after any type of new introduction.

Patience and time are key: TAKE IT SLOW AND LET IT GROW!