• 4.0 to 10.0 mm coarse grain - large enough that a determined digger rearranges the bed rather than excavating a crater down to the glass.
• Aragonite based - it adds calcium, magnesium and carbonate to the water, and CaribSea states it buffers automatically for the life of the aquarium.
• Live bacteria in the bag - supplied damp and biologically active, which shortens the time a new bed takes to start processing ammonia.
• No rinsing - it is packed in a water conditioning solution that removes chlorine and chloramine. Rinsing throws away both the bacteria and the conditioner.
• The lightest cichlid grade per litre of bed - at 54 lb per cubic foot it takes about a quarter fewer kilograms to fill the same bed as the 72 lb per cubic foot Cichlid Gravel.
• Black throughout - most Rift Lake cichlids hold deeper colour over a dark substrate than over a white one.

This is the question a substrate page has to answer. The table gives the weight of Black Cichlid and the number of 9.072 kg bags for common Australian tank footprints, worked from CaribSea's published bulk density of 54 lb per cubic foot (0.87 kg per litre of bed).

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 and caves sitting on the glass displace substrate, so a heavily scaped Tanganyikan 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 Eco-Complete White Cichlid if you want a bright bed rather than a dark one.

Black Cichlid and Cichlid Gravel share the same 4.0 to 10.0 mm grain, but Black Cichlid is 54 lb per cubic foot against the gravel's 72. That means a lighter, more porous grain.

The upside is fewer kilograms and less freight for the same bed depth. The downside is that a large digging Malawi or a nest-building featherfin shifts a lighter grain more readily. If your tank is built around serious excavators, the denser gravel stays put better.

Suitable for: Lake Malawi, Lake Tanganyika and Lake Victoria cichlid aquariums; Central American cichlid tanks that want hard alkaline water; any freshwater setup where pH drifts down between water changes and you would rather it did not.

Not suitable for: planted aquariums, soft-water community tanks, blackwater and Amazonian setups, shrimp tanks, and discus or apistogramma systems. Aragonite raises pH and carbonate hardness and there is no way to switch that off. It is also the wrong grade for shell-dwelling Tanganyikans, which need a fine sand they can actually excavate - Eco-Complete Cichlid Sand at 0.5 to 1.5 mm is the right call there.

1. Put the substrate into an empty tank first, and tip in the liquid from the bag with it - that liquid is the water conditioner and the bacterial culture.
2. Level it, then place rockwork and caves directly on the glass wherever you can, so nothing topples when a fish digs underneath.
3. Add water slowly onto a plate or a bag laid on the substrate rather than straight onto the bed.
4. Run filtration. Some cloudiness is normal and clears as the filter catches the fines.

A 4.0 to 10.0 mm bed has large gaps between grains, so uneaten pellets and detritus fall into it rather than sitting on top. This grade rewards a proper gravel vacuum worked into the bed at water changes, not the light surface siphoning a fine sand gets.

Keeping the bed shallow is what makes that possible. At 2.5 to 5 cm you can reach the glass with a siphon. Much deeper and the lower layer becomes a detritus reservoir you cannot service.

The buffering capacity is consumed very slowly as aragonite dissolves, so there is no replacement schedule. Top up if the depth drops noticeably over several years.

• CaribSea Eco-Complete Cichlid Sand - the fine grade, for a sand patch in front of the rockwork or for shell dwellers.
• Dragon Stone Freshwater Rock - pitted rock that makes good cichlid caves and territory breaks, and reads strongly against a black bed.
• Hikari Cichlid Excel Pellet 250g - a vegetable-based pellet for the herbivorous Malawi species usually kept over this substrate.

CaribSea does not publish a warranty term for its substrates. Your rights under the Australian Consumer Law apply regardless, 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 five bags, close to 45 kg, so check the freight total before you order a full bed.

Do I need to rinse CaribSea Eco-Complete Black Cichlid before use?

No. It is supplied damp in a water conditioning solution with live bacteria, and CaribSea's instruction is to place the contents straight into the aquarium. Rinsing removes the conditioner and the bacteria you paid for.

How high will it push my pH?

Aragonite buffers against downward drift rather than driving pH to a fixed target, so the figure you land on depends on your tap water, your KH and how heavily the tank is stocked. It will hold a Rift Lake tank in the alkaline range and stop the slow acidification that otherwise happens between water changes.

What is the difference between Black Cichlid and Cichlid Gravel?

Grain size is identical at 4.0 to 10.0 mm. The differences are colour and density: Black Cichlid is black and 54 lb per cubic foot, Cichlid Gravel is natural toned and 72 lb per cubic foot. The black grade needs fewer kilograms for the same bed but is moved more easily by large diggers.

Can I use it in a planted tank?

No. It raises pH and carbonate hardness, which suits Rift Lake cichlids and works against most aquarium plants. For a planted tank use Eco-Complete Planted Black, which is carbonate free and will not raise pH.

Is the black colour a coating that wears off?

CaribSea states its Eco-Complete substrates use no artificial dyes, paints or chemical coatings, so there is no painted surface layer to chip away from individual grains.

How deep should the bed be?

2.5 to 5 cm suits most Rift Lake tanks and stays serviceable with a gravel vacuum. Go deeper only where a species genuinely digs, and accept that the lower layer will collect detritus you cannot easily reach.