vivid colours, patterns and behaviour of marine fish compared to freshwater fish, they are still reasonably popular. The advances in filtration technology and increase in available knowledge on how to maintain marine fish as well as the increasing number of aquarium-bred species is seeing a gradual rise in their popularity. Coral reef tropical fish Many marine tropical fish, particularly those of interest to fishkeepers, are those that live among or in close relation to coral reefs. Coral reefs form complex ecosystems with tremendous biodiversity. Among ocean inhabitants, tropical fish stand out as particularly colorful. Hundreds of species can exist in a small area of a healthy reef, many of them hidden or well camouflaged. Reef fish have developed many ingenious specialisations adapted to survival on the reefs. Some recreational scuba divers keep lists of fish species they have observed while diving, especially in tropical marine environments. Coral reefs occupy less than 1% of the surface area of the world oceans, yet they provide a home for 25% of all marine fish species. Reef habitats are a sharp contrast to the open water habitats that make up the other 99% of the world's oceans. However, loss and degradation of coral reef habitat, increasing pollution, and overfishing including the use of destructive fishing practices, are threatening the survival of the coral reefs and the associated reef fish. References Aquariums