Saltwater Aquarium Substrate Ideas

Substrate is what lays on the bottom of any aquarium and serves several different purposes: it can be aesthetic, giving your aquarium a naturalistic (or decorative) look or it can be practical, providing space for beneficial bacteria to grow, raising the pH of your water or capturing dirt and other harmful particles. There are essentially three types of aquarium substrates for a saltwater aquarium, each with their own benefits.

  1. Gravel

    • Gravel is one of the most common substrates for most freshwater aquariums, though it is rarely seen in saltwater aquariums. Gravel, which is essentially tiny pebbles similar to the types seen on the bottom of rivers, creeks or streams, should only be used in fish-only saltwater aquariums containing hardy saltwater fish like clownfish or damsel fish. Gravel adds very little chemical benefit to aquarium water besides providing a place for beneficial bacteria to grow. It doesn't raise the pH or provide a home for small copepods needed in more advanced reef aquariums.

    Aragonite Sand

    • Aragonite sand is commonly sold as "reef sand" and comes in several different varieties that differ, for the most part, in size, with some aragonite sand being sandy and powdery (sugar-sized sand) and other types being coarser. Aragonite sand has the benefit of providing space for copepods to propagate, which can feed your saltwater aquarium's pickier inhabitants. Smaller-grained sand should be used if you're planning on filling your aquarium with sand-sifting animals like gobies, starfish or sting rays, while coarser sand should be used with middle and top-dwelling animals.

    Crushed Coral

    • Crushed coral is one of the most common saltwater aquarium substrates and is composed of the crushed remains of long-dead coral. This substrate comes in a variety of different colors, some of which can be very vibrant like red or green while others may be more natural. Crushed coral has the additional benefit of raising the pH of water, as a necessary parameter for most saltwater animals is a pH of 8.1-8.5, much higher than the standard 7.0 found in most freshwater aquariums.