pensate for these thermal and moisture loads. Macroenvironmental relative humidity levels are generally defined by safety issues and staff comfort, since room humidity is not critical for aquatic species; however, excessive moisture may result in condensation on walls, ceilings, and tank lids, which may support microbial growth and serve as a source of contamination or create a conducive environment for metal corrosion. In a dry environment (e.g., indoor heating during cold weather or outdoor housing in some climates/seasons), evaporation rates may be higher, potentially requiring the addition of large quantities of water to the system and monitoring for increases in salinity/conductivity, contaminants, or other water quality aberrations. Some amphibians and reptiles may need elevated microenvironmental humidity (in excess of 50-70% relative humidity), which may require maintaining elevated macroenvironmental humidity levels (Pough 1991; St. Claire et al. 2005).
Room air exchange rates are typically governed by thermal and moisture loads. For fish and some aquatic amphibians, the microenvironmental air quality may affect water quality (i.e., gas exchange), but appropriate life support system design may reduce its importance. Airborne particulates and compounds (e.g., volatile organic compounds and ammonia) may dissolve in tank water and affect animal health (Koerber and Kalishman 2009). As the aerosolization of water can lead to the spread of aquatic animal pathogens (e.g., protozoa, bacteria) within or throughout an aquatic animal facility, this process should be minimized as much as possible (Roberts-Thomson et al. 2006; Wooster and Bowser 2007; Yanong 2003).
Aquatic and semiaquatic species are often sensitive to changes in photoperiod, light intensity, and wavelength (Brenner and Brenner 1969). Lighting characteristics will vary by species, their natural history, and the research being conducted. Gradual changes in room light intensity are recommended, as rapid changes in light intensity can elicit a startle response in fish and may result in trauma. Some aquatic and semiaquatic species may need full-spectrum lighting and/or heat lamps to provide supplemental heating to facilitate adequate physiological function (e.g., aquatic turtles provided with a basking area; Pough 1991).
General concepts discussed in the Terrestrial Animals section apply to aquatic animals. These animals may be sensitive to noise and vibration, which are readily transmitted through water. Species vary in their response and many fish species acclimate to noise and vibration, although