# Rearing Conditions and Automated Feed Distribution Systems for Zebrafish (_Danio rerio_)
## 5 Automated Feeding Systems  
In the last decades, both (from) single research groups and (to) biotech companies have developed automated systems for zebrafish including feeders. This has been accomplished to meet adequate rearing and nutrient conditions, improve zebrafish health and welfare, and implement new tools in the culture facilities to reach standardization and/or removal of human error factors. Specifically, in the field of feeding supply, attention has been given to standardize feeding practice, including feeding ratio, frequency, and time, that matches digestive biology and normal feeding behavior of zebrafish. As mentioned above, feeding and feed management practices have many and critical implications for the success of rearing zebrafish in a facility. Moreover, the simple act of daily feeding zebrafish in a facility with hundreds or even thousands of individual tanks has many important practical implications, from growth and reproductive performance of the fish stocks to the percentage of labor devoted to carrying out such operations [27]. Feeding management also impacts fish welfare and health in captivity as well as reproducibility and statistical reliability of results obtained by different laboratories. Therefore, the development of standardized systems is increasingly needed, and greater attention to improve the knowledge of physiological and behavioral basis and a constant monitoring is required. The behavior related to feeding management has been shown to be highly affected by the circadian rhythms, which are endogenous and persistent rhythmic activities under constant environmental conditions driving the synchronization of feeding rhythm and locomotor activity to feeding regime. In this context, zebrafish has already been widely used in different studies, including daily rhythms of locomotor activity in adults and larvae [85], synchronization of activity rhythms to light and temperature cycles [86], and daily rhythms of reproduction [83]. Searching for food, for example, usually takes place when the abundance of prey increases and the risk of predation is reduced [87], and, from a physiological point of view, the nutrient search and utilization mostly depend on the digestive and metabolic states of the fish [88]. In this context, swimming and locomotor activities are probably two of the most widely studied behavioral variables [30] which, coupled with the feeding rhythm, are found to be highly affected by light. For this, both variables represent two main behavioral factors determining feeding time in many fish species [83]. Thus, [PERSON] et al. [87] developed a new self-feeder system with a food-demand sensor suitable for zebrafish to investigate the daily pattern of feeding and locomotor activities, their endogenous nature under constant conditions, and their synchronization to feeding regime. The observations indicated that zebrafish usually display nocturnal feeding rhythms, whereas the locomotor activity rhythms are located mostly in the diurnal range. In the context of home aquaria, where the number of individuals and cages to feed in captivity is more reduced, automated and practical equipment allowing for the control the delivery of food amounts, such as rotating barrel fish feeder and peristaltic pump, have been commercialized. However, when such devices are translated from small-scale to large-scale systems, their inefficiency and limitations emerge, which are, among others: (i) one feeder needed for one tank, thus resulting in a difficult application to housing systems composed of hundreds of tanks; (ii) not eliminating the need of cleaning a large number of devices on a daily-to-weekly basis, which may result in a very time-consuming and high-cost labor activity; and (iii) feeder(s) needed to be set to control different granulometry feeds.