The tilapia (oreochromis niloticus) industry produces 7 million tons of fish worldwide, and only 5% of it is produced in the U.S. There is a demand to significantly improve hatchery water quality in order to stimulate successful hatching in incubator systems that hatch and produce fry. Recirculating aquaculture systems can provide a better outcome for mass production of t ilapia, because they allow for more control over the system’s environment . RAS facilitates isolation of batches and the year-round growth of fry. This paper addresses the rationale used to size biofilters for this application, based on tilapia’s high tolerance for ammonia and pH impact, and egg loading and biofouling behavior. Sizing strategies and criteria for floating beads bio- clarifiers and moving bed reactor systems are discussed. Additionally, this paper provides a developed tilapia-specific equation for sizing biofilters for hatching and fry. Based on BOD5 of 0.75 ± 0.01 g/g, nitrogen loading of 11.67 ± 0.31%, and protein loading of 73.10 ± 0.42 %, the sizing criteria for a PolyGeyser® RAS is determined as a function of the volume of bead media needed for tilapia-specific egg weight and TAN.