Collection: Marine Substrates

Aragonite Rather Than Gravel

Saltwater substrates here are aragonite-based, the same calcium carbonate material found on natural reef flats, rather than the inert gravels used in freshwater tanks. What separates one bag from another is grain size, bag weight, and whether the substrate is meant for the display or the refugium.

Grades and Where They Work

• Fine oolite — smallest grain size, bright and soft in appearance, best under gentle flow.
• Special grade sand — medium grain, the common all-purpose choice for reef displays.
• Crushed coral — coarse grade that stays put under strong flow and siphons easily.
• Bacteria-seeded sand — packed wet so the bag goes straight in without rinsing.
• Mineral mud — a refugium substrate, not intended for a display bed.
• Alternative marine sands — supplied by the kilogram for smaller builds.

Setting Up the Bed

Decide on depth before ordering. A shallow bed of about an inch is the easiest to keep clean, while deeper beds cost more, weigh more, and need more attention over time. Rinse dry sand until the runoff is clear before it goes in; wet-packed bags need no rinsing and are poured in as supplied. Set your rockwork directly on the tank bottom and pour the sand around it rather than building on top of the bed, so that burrowing fish cannot undermine the structure later.