# Rearing Conditions and Automated Feed Distribution Systems for Zebrafish (_Danio rerio_)
## 1 Introduction  
Zebrafish (_Danio rerio_) is a freshwater teleost (ord. Cypriniformes; fam. Danionidae) that has been used in home aquaria for many years; however, during the last three decades, it has become a key model in a variety of human-biology-related research areas, from biomedicine to toxicology [1, 2], from human diseases to therapeutic drugs screening [3, 4]. Its use back to fish biology as a tool for complementing research in aquaculture and commercial fish production processes [5, 6] has enhanced and further extended its experimental relevance as an animal model. Zebrafish genome shares a high degree of synteny with both lower and higher vertebrate (from teleost fish to human) genomes [7, 8]. Its sequence is fully accessible [9], a condition shared by many other teleost fishes, e.g., Japanese fugu (_Fugu rubrips_), green-spotted purfferfish (_Tetraodon nigroviridis_), medaka (_Orzyzias latipes_), or three-spined stickleback (_Gasterosteux aculeatus_). Moreover, various established approaches in genetic manipulation make zebrafish transgenic lines available to date [10, 11]. Among fish models, zebrafish is most likely the only one offering a very complete panel of experimental advantages, such as easy rearing and breeding in captivity, including very short generation time (\(\approx\)3 months), large number of eggs (100-200 eggs/clutch), transparency during egg and larval period, and maturation of organogenesis in the larval stage (i.e., organs and systems are all functional making the larva physiologically comparable to the adult) [12]. The advantages of the experimental model go together with a community of zebrafish researchers spreadworldwide and a robust and rather advanced technological support on the zebrafish-rearing aquaria systems. Recently, zebrafish has started to emerge as a model for evaluating the direct effects of administered dietary components on functional diet-gene interactions and for exploiting novel approaches in nutrigenomics, nutrigentics, nutritional physiology, and immunity [13]. In fact, depending on their presence, availability, and storage, dietary compounds can temporarily alter gene and protein expression (e.g., acting as co-factors within the relevant metabolic systems). These effects are more relevant in poorly stored nutrients such as water-soluble vitamins. Additionally, they can have longer lasting impacts on gene expression as essentially permanent genome alterations, which can occur, for example, for dietary components altering mutation rates or genome methylation patterns [14]. In addition, in this context, dietary amino acids have been shown to be effective in zebrafish [15,16]. On the other hand, variations in individual genetics can affect nutrient needs and tolerances, requiring individualized diet recommendations [14]. Taken together, the results obtained in zebrafish could be translated to aquaculture nutrition research and to relevant commercial species, such as Atlantic salmon (_Salmo salar_), rainbow trout (_Oncorhynchus mykiss_), common carp (_Cyprinus carpio_), Nile tilapia (_Oreochromis niloticus_), among others. However, such translation requires in-depth comparative knowledge on the physiology and the biology of the species in question to assess the compatibility of the translation. Despite the zebrafish use worldwide in the laboratory, the standardization of its rearing conditions, including daily nutritional requirements and good feed management practices, is still poorly studied [17]. To some extent, this is surprising when compared with what is available for other animal models, including terrestrial vertebrates such as rodents [18], or aquatic species such as tilapia [19], channel catfish (_Ictalurus punctatus_) [20], or common carp [21], among others.