Collection: Marine Substrates

Aragonite, Crushed Coral and Mud

Marine substrates here are aragonite-based rather than inert gravel, so they suit reef and fish-only saltwater tanks alike. The practical differences between them come down to grain size, bag weight and whether the sand is packed dry or wet.

Choosing a Grade

• Fine oolite — the smallest grain, bright and soft-looking, best in tanks with gentle flow.
• Special grade reef sand — mid-size grain, the usual default for mixed reefs.
• Crushed coral — coarse, resists blowing into drifts, and easy to siphon around.
• Bacteria-seeded sands — packed wet in 5lb to 40lb bags for a faster start.
• Mineral mud — a refugium-specific substrate rather than a display sand.
• Bio sand — an alternative marine sand supplied by the kilogram.

Getting It Into the Tank

Work out your bed depth before ordering: a shallow bed of roughly an inch is easiest to keep clean, while deeper beds are heavier on both budget and maintenance. Dry sands should be rinsed until the water runs clear; wet, bagged sands are supplied ready to go in. Whatever you use, put the sand down first and set your rock on the glass beneath it, never on top of the bed — rock resting on sand can be undermined by burrowing fish and shift months later.