• 0.25 to 3.5 mm fine grain - fine enough for sand-sifting fish to work through, and fine enough to read as a solid dark surface rather than dark gravel.
• Live bacteria supplied in the bag - the sand arrives damp and biologically active, so a new bed starts processing ammonia sooner than dry sand would.
• No rinsing - CaribSea's instruction is to tip the bag straight into the tank. Rinsing washes out the bacteria you paid for.
• Dark background for colour - fish that pale over a light substrate generally hold deeper colour over a dark one, and coral fluorescence reads more strongly against black.
• Buffers pH and alkalinity - it is aragonite, so it adds carbonate rather than consuming it.
• Clears quickly - CaribSea states a properly filled tank begins clearing within hours and is completely clear in 24 to 48 hours.

Hawaiian Black is the lightest of the three live grades at 80 lb per cubic foot (1.28 kg per litre of bed), so a given depth costs fewer kilograms than the same depth in Bimini Pink. The table gives the weight and the number of 9.072 kg bags for common Australian tank footprints.

How these figures are worked out

CaribSea publishes a bulk density for every substrate. Bed volume is the tank footprint multiplied by the depth you want, and the weight is that volume multiplied by the density. Bag counts are rounded up to the next whole bag.

Two practical adjustments. Rockwork sitting on the glass displaces sand, so a heavily aquascaped tank needs a little less than the table says. A bed that slopes from front to back needs the average depth, not the deepest point.

We also stock CaribSea Arag-Alive Fiji Pink and Arag-Alive Special Grade Reef if none of the four above is the grain size you are after.

Two things are worth knowing before you commit. Detritus, uneaten food and dislodged coralline flakes are all pale, and they show against black in a way they never do against a pink or natural bed. The bed looks dirtier at the same actual cleanliness.

The second is flow. At 1.28 kg per litre this is the lightest grade of the four on this page, and the grain starts at 0.25 mm. A powerhead pointed at the substrate will scour it more readily than it would scour Bimini Pink. Aim flow across the bed, not into it.

Suitable for: marine fish-only and reef aquariums where you want maximum contrast; tanks with sand-sifting gobies, wrasses or jawfish that need a fine grain; hard, alkaline African cichlid tanks; refugium beds.

Not suitable for: planted freshwater tanks, soft-water community aquariums, and blackwater setups - aragonite will raise pH and carbonate hardness and there is no way to stop it. It is also the wrong choice directly under a downward-facing powerhead, where the fine fraction will be excavated.

Light siphoning of the top layer at water changes keeps the pale detritus that shows up against black under control. A turkey baster used to puff detritus off the surface before a water change works better than dragging a gravel vacuum through the bed.

Beds over about 5 cm deep are best left undisturbed below the surface. The sand itself does not need replacing on any schedule.

• CaribSea Life Rock Shapes - pale aquascaping rock, which is the contrast black sand is bought for.
• CaribSea Arag-Alive Bimini Pink - the coarser alternative if scouring is a concern in your tank.
• Red Sea Salt 10 kg - for mixing the water that goes in over the bed.

CaribSea does not publish a warranty term for its substrates. Your rights under the Australian Consumer Law apply regardless of that, and are not limited by anything the manufacturer does or does not offer.

Each bag weighs 9.072 kg. A 150 x 60 cm tank at 5 cm depth is seven bags, a little over 63 kg, so check the freight total before ordering a full bed.

Does black sand show dirt more than light sand?

Yes. Detritus, uneaten food and shed coralline flakes are pale and stand out against a black bed. The bed is not dirtier than a light one at the same maintenance level, but it reads that way, so most people siphon the surface more often.

Is Hawaiian Black fine enough for a sand-sifting goby?

Yes. The grain runs from 0.25 mm, which is fine enough for sifting gobies and wrasses to pick up and pass through their gills. The coarser 3.5 mm fraction is a small part of the mix.

Do I rinse it first?

No. CaribSea's instruction for all Arag-Alive sands is to place the contents straight into the aquarium. Rinsing removes the live bacteria and defeats the purpose of buying a live sand.

Is the black colour natural or a coating?

Arag-Alive Hawaiian Black is supplied as a black aragonite substrate, not a coated or painted one, so there is no coating to chip off individual grains over time.

Can I mix Hawaiian Black with a lighter CaribSea sand?

You can, and the grades are chemically the same aragonite. Be aware that flow gradually sorts mixed grades by weight and grain size, so a deliberate two-tone bed usually ends up blended after a few months.

How deep should I go?

2.5 to 5 cm is the usual shallow bed and is straightforward to maintain. Beds of 7.5 cm and deeper are a deliberate denitrification strategy and should be left undisturbed once established.