Choosing sand/substrate for your reef tank used to be a simple choice, but now there is a wide variety of options that can be confusing. In this article, we will discuss the available options and provide insights and guidance on choosing the best substrate to suit your particular reef tank.

Sand or Substrate

When people talk about substrate for their reef tank, they can actually be referring to many different products, as substrate can be thought of as a collective term that encompasses many different items. The term substrate actually means the surface or material that allows an organism to grow from. Popular substrates found today are typically crushed coral and aragonite.

The Advantages of Substrate

Reef tank substrate has several purposes to build and maintain a healthy ecosystem inside your tank.

1. Aesthetics
   Many people will try to emulate the look of a real coral reef. By using a carefully chosen substrate combined with rocks and corals, you will have an authentic looking reef.
2. Biological filtration
   The substrate and rocks provide a home for the good bacteria in your tank to thrive. This provides a biological filter to extract unwanted things from the water in your tank.
3. Home
   Some types of tank inhabitants like to burrow in the substrate or make a home in it. Examples are snails, shrimps, crabs, worms and even some fish.

Types of Substrate

1. Crushed Coral
   While initially looking similar to sand, on closer inspection you can see that crushed coral contains much larger individual particles than sand by comparison. These particles consist of pieces of stones and crushed up coral skeletons. Crushed coral contains calcium, which in turn will contribute to feeding your corals. One negative aspect to this type of substrate is that due to the relatively large particles, some burrowing animals may struggle to burrow through it.
   
2. Aragonite
   This is the typical sand that most people think of, small grains of beige and/or white. Similar to crushed coral, Aragonite sand contains coral skeletons and therefore also contains calcium carbonate. As the water slowly dissolves the particles of sand, calcium carbonate is released into the tank which is absorbed by corals.
   

Dry or Live Substrate

A common question that crops up when making a decision on substrate is whether or not to go for “dry” or “live” substrate. An established reef tank will contain a thriving colony of good bacteria within the substrate. The decision to use “live” over “dry” is how quick you need a new reef tank to establish the colony of bacteria and create a biological filter. You can reduce the cycling time of a new tank effectively by using “live” substrate. This type of substrate already has living colonies of bacteria already in it.
You can think of “live” substrate as a time saving product, and it is way more expensive than “dry” substrate for this reason. Dry substrate is substantially cheaper, and if you are not in a rush to get a new tank up and running and fully cycled, then this is a good option.

Amount of Substrate

The majority of reef tank owners will go for 1 to 2 inches of substrate, this seems to be the popular choice and avoids issues that can occur with deeper or shallower levels. To calculate how much substrate you need to buy, you can use a simple formula of 1 pound of substrate per gallon of water. So for example; if you had a 32 gallon tank, you would need approximately 32 pounds of the substrate to get about 1 inch of level substrate across the base of the tank.

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