Introduction
Between 1.5 and 2 million households worldwide are believed to keep tropical marine aquaria and the collection trade which supplies this industry is estimated at US$220-330 million annually (Wabnitz et al., 2003). The majority of these imports are destined for the United States, Europe, and Japan (Chapman et al., 1997).
Unlike freshwater aquaria species, where 90% of fish species are farmed, only 100 of the 800 species traded in the marine ornamental industry are captive-bred. The family Pomacentridae, particularly clownfish species of the genus Amphiprion, represents the most important group of captive-bred marine species.
Among all species, Amphiprion sp. is the best known to aquarium traders due to its color pattern, interesting behavior, and robustness. From 1997 to 2002, A. ocellaris was the most common species of marine ornamental fish and made up 15.6% of the total number exported worldwide and over 25% into European countries (Wabnitz et al., 2003).
One of the major drivers of growth in the fish-keeping hobby over the last 50 years is the development of commercially available manufactured feed. The acceptance and reliance of the mainstream hobby on manufactured feeds has turned attention to the need to quantify the nutritional requirements of these fish (Sales and Janssens, 2003).
The quality of feeds is not only an issue in the day-to-day husbandry of these animals but also in their large scale production. With the intensification of modern ornamental fish production, a supply of nutritionally-balanced and affordable feeds is required.
The aquarium industry is relatively small despite its very high value, thus few studies on the nutritional requirements of ornamental fish have been published (Priestley et al., 2006a,b,c). A main problem within the trade is the diversity of fish kept in home aquaria, each with its own nutritional requirements.
Nutrient requirements have often been quantified by dose-response relationships (Elangovan and Shim, 1997; Kruger et al., 2001; Ling et al., 2006) but this approach is time consuming and limited in application.
In the following study, an attempt was made to apply a factorial approach for determining feed requirements for ornamental fish such as A. percula. The method itself was successfully applied to determine requirements in farmed fish (Lupatsch et al., 2001; 2003a,b; Lupatsch and Kissil, 2005).
The advantage over the more traditional empirical based dose-response methods is that it can be used to describe protein and energy requirements for growing fish throughout the production cycle.
Estimations are not necessarily restricted to within the size range of the test species and, so, are applicable to a broad range of fish. Key to achieving this however is establishing the utilization efficiencies and maintenance requirements for protein and energy, an assessment of the whole body composition as a function of fish size, and growth potential of the target species under a given set of culture conditions.
