Cichlids are a large, diverse group of fish. Some have such beautiful coloration that it is said their colors rival those of saltwater fish. With this in mind, you can consider adding fake corals and other decorations to simulate the decor of a saltwater tank with freshwater fish.
Sand and Base Rock
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Most saltwater fish tanks have coral sand substrate and "live rock," or dead coral colonized by other animals. For African Rift Valley cichlids, you can use many of the same substrates and rocks you would find in a saltwater tank. Coral sand and other calcium-rich rocks will harden the water, making it more like the water they come from. For other cichlids, you can use white aquarium sand and large, rough white rocks to get the same effect without altering your water.
Fake Coral and Seaweed
texture of the sea coral. image by Olga Khoroshunova from Fotolia.com
Fake seaweed and coral have gotten more and more realistic. You can purchase plastic and silicone coral, seaweed and other invertebrates. Many are designed to mimic specific saltwater species. These are intended for saltwater tanks, but there's no reason you can't use them in a tank with cichlids. You can create a whole reef tank using fake coral, and the average person will not be able to tell the difference.
Invertebrates
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While African Rift Valley cichlids and larger cichlids will probably eat them, some smaller cichlid like the krib and the ram may get along fine with aquarium invertebrates. Freshwater shrimp, crabs and snails can look very similar to their saltwater counterparts. Research any invertebrate you keep. Some may attack fish and others may face getting eaten themselves. For example, an oscar (a large South American cichlid) may consider a crayfish a tasty snack, while the same crayfish could eat a prized ram cichlid.
What to Avoid
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If you want to safely imitate a saltwater tank, you want to avoid several things. First, avoid actual coral skeletons as they are often harvested at the expense of coral reefs. Plastic coral look more lifelike than dead real coral anyway. Also, avoid the types of novelty ornaments you would see in a freshwater tank, like plastic castles and divers. You never see these in saltwater tanks. Last, avoid fake (or real) freshwater plants. These give a tank a very freshwater look.