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so may not be suitable in a tank with other fish in it. Some fish that live in fast rivers, though, have flattened bodies to enable them to live on the bottom without being swept away by the current; these may be more suitable subjects for the aquarium. Species that live in still water exhibit still other adaptations to their environment. Although these types of fish are not in danger of being swept away by the current, they may be vulnerable to attacks by other fish, so camouflage is often quite important. Some have markings that look striking when isolated in an aquarium but help the fish blend in with surrounding vegetation in their natural habitat. Many fish have vertical stripes that make them attractive to the human eye, but these markings actually serve to help the fish merge visually with the stems of reeds or pond weeds. Likewise, fish with thin bodies can swim easily between plant stems but when viewed from the side they have a distinctive

appearance that makes them a good choice for an aquarium. Although camouflage is important to many fish, the need for cryptic markings is sometimes superseded by the need to attract a mate or warn off a rival. Fish that are able to escape from danger easily or ward off predators by attacking them can usually afford to have bright colors and striking body shapes. In some species, it is only the males that have the elaborate body forms or colors, whereas the females have more subdued markings. Many young fish lack the distinctive appearance of the adults. Because they are small and inexperienced, they need extra protection to survive; until they reach their full size they have markings that help them hide from danger. Although to human eyes some features may appear to be unnecessarily elaborate or extravagantly colored, they have developed that way over the course of thousands of years of slow evolution to suit the individual species and its way of life.

The large aquarium and continuous supply of live food required by fish such as this dragon moray eel, Muraena pardalis, make keeping species like this a possibility only for enthusiastic specialists and public aquaria.

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