One very crucial step in the decorating process of our cichlid tank is choosing the correct bottom material. Many new people to the cichlid keeping hobby have no real idea what to use as substrate and let themselves guide by appearance and alleged qualities. At best, they choose naturally looking grey-brown small gravel that's sold at a reasonable price by the local fish store (LFS). Other frequently sold materials are:
*Fancy black or bright white gravel/sand. Mostly bought out of ignorance and just for the 'great' look.
*Special African cichlid pacific gravel mixes, that are heavily overpriced and sold as the nec plus ultra to people who believe that the most expensive stuff is the absolute best.
*Crushed coral, originally used in reef tanks and very popular in the US, where it's often (mis)used in cichlid tanks because of its reputation of maintaining a high pH. The only good way to use this material, is putting it in an external canister where it is in the path of the water, thus being much more effective. Also a more reliable way of maintaining a high 'rift lake' pH is adding baking soda (NaHCO3) with each water change.
*Colored gravel, luckily very rarely used, guarantees a cheap disco effect.

Construction sand in my tank, bought in a DIY shop for only 2€/50Kg or about 2$/100lbs.

But do we need all these prewashed prepackaged and cleverly marketed materials? If you want to mimic the lake's biotope as close as possible, the answer is NO. You don't even have to travel to Lake Malawi to see what can be used as a substrate. Just take a look at the underwater pictures in Ad Konings books to see what our cichlids really need: ordinary cheap SAND!!! The fish in the lake are closely adapted to this specific substrate for collecting food and breeding, a result of an evolution of millions of years, where only the fittest and best-adapted cichlids survived periods of severe food shortage. Decorating your tank with sand simply helps bringing out their most natural behaviour, a feast for the hobbyist's eye.
Food: Aulonocara's “listen” to the bottom with the enlarged senses on their head, the “aulos”. When a prey moves, the Aulonocara localizes this, using the “aulos” like a sonar and then dives into the sand grabbing the invertebrate or crustacean. Other fish that use the sand are (taenio)Lethrinops sp., small Mylochromis sp. and Fossorochromis rostratus which dive into the sand, take a bite of it and sift it through their gills for insect larva, invertebrates or crustaceans.

Breeding and nest building: Have you ever seen the pictures of male Malawi cichlids above their sand nest? Fossorochromis rostratus and (taenio)Lethrinops build a huge crater with a diameter of up to 2.5m. This can’t be displayed in our aquariums which are obviously too small for that. Some Mylochromis sp. and Nyassachromis sp. build smaller craters. In the middle of that crater you will only find fine sand which cannot be confused with eggs. The larger gravel is put away to the edge and this is what makes the circle look like a crater. Some other species which need less space to exhibit their natural behavior like Protomelas, Copadichromis, Otopharynx, Cyrtocara or Sciaenochromis also pay much attention to their nest: the coarse material (which might be confusing for the female since it resembles eggs) is removed until only fine sand remains. I’ve also seen the nest building of the Copadichromis Borleyi which carries the fine sand up on a rock where it forms a thin breeding carpet. In a 'gravel only' tank these cichlids dig until they reach the glass bottom, simply because the gravel is too large, thus egg confusing.

Hiding: Some sand-dwelling cichlids like Fossorochromis rostratus and Lethrinops sp. have developed a successful surviving strategy. They dive in the sand quick as lightning when they feel threatened (catch or net them). Shortly after, they come out and swim as if nothing happened. Can you imagine what would happen when such a fish would like to hide under gravel? It could get injured. Never try this for fun, as it is stressing for the fish.

A male C. azureus has built a magnificent nest in the middle of my 3000L tank.

What kind of sand should we use? The cichlids are actually too forgiving as they try to make the best of all bottom materials they're offered, but it’s better to avoid bright white material as it tends to give the cichlids a washed out look. A greyish and light brown substrate does just fine. Be sure to use sand with a good variation in grain size, so it won't compact. I bought construction sand, actually plain river sand, which is sold in a DIY shop for only 2€/50Kg or about 2$/100lbs. This material should be washed thoroughly to remove the clouding dust and contamination, just like all aquarium decoration. If you want to be sure the sand is disinfected you can always boil it, so you’re also sure all harmful soluble parts are gone.

Lethrinops microstoma using the sand to clear its gills.

The maintenance is not that difficult but takes a little time. You can perform a partial cleaning with every waterchange.
This way you reduce the piling up dirt load and prevent the water from getting a yellowish color through dissolved waste, which results in a less fast saturation of activated coal.
You only need one or more large buckets and a garden hose. The sand near the window is removed together with dirt in the first filter compartment where the most detritus settles down. Also places with stagnating water flow, mostly depressions near rocks, need to be cleaned. After this the glasses are cleaned. The buckets are moved to a place where you can rinse it safely without flooding the house. Also pay attention not to hurt your back beause such a bucket weighs a lot! I'm aware that not everyone has such a monster aquarium but I use a pump to change the water. The outlet of it develops enough pressure to rinse the sand in the buckets. This rinsing is repeated until no more waste comes off and when finished the sand can be put back in the aquarium before it's filled again.

Although one can never come up with "defaults" still it's recommended that you use plain river sand for all your African Rift Lake Cichlid tanks. The bottom line is: The more your aquarium resembles the lake, the more you get rewarded with the natural behaviour of the amazing Malawi cichlids, which is always a worthy spectacle.