Unlike many popular freshwater fishes that naturally live from one wet season to the next, reef fish are built to last. In the wild, the highest mortality rates occur when young fishes settle out of the plankton and have to find a territory of their own - failure results in either predation or starvation. This is why it is always preferable to select small individuals when choosing your marine fish, as this 'post-planktonic recruitment' represents a surplus of youngsters that would naturally fall prey to selection pressures in the wild, rather than removing key breeding adults vital to a healthy population.
Once they have a territory and food source, predation is the greatest issue facing the average reef fish and often the combative nature of fishes such as Damsels means that they can recover from physical traumas that would otherwise prove fatal to less robust freshwater species. There are few marine equivalents of the 'live fast - die young' Livebearers, Tetras and Killifishes seen in home aquaria and so teenage aquarium fish are commonly seen in well maintained reef tanks.
By preventing premature deaths due to water quality, disease or aggression, you can stand a good chance of seeing your reef fish grow to a ripe old age of around ten years for all but the smallest reef fish.
At this point it is timely to add that a number of specialised feeders have no place in the home aquarium and often fail to thrive in aquaria. Species such as Sweetlips, Coral-eating Butterflyfishes and Redfaced Batfish will normally fail to thrive and suffer greatly reduced life expectancies in captivity. This is why we do not agree with their importation and avoid stocking them in our stores.