these may cause subclinical effects (Smith et al. 2007). Vibration through floors can be reduced by using isolation pads under aquaria racks. Some facilities elect to place major components of the life support system (e.g., filters, pumps, and biofilters) outside the animal rooms to reduce vibration and noise.

The primary enclosure (a tank, raceway, pond, or pen holding water and the animal) defines the limits of an animal’s immediate environment. In research settings, acceptable primary enclosures

• allow for the normal physiological and behavioral needs of the animals, including excretory function, control and maintenance of body temperature, normal movement and postural adjustments, and, where indicated, reproduction. In some poikilothermic reptiles and amphibians, microenvironmental temperature gradients may be needed for certain physiologic functions such as feeding and digestion.

• allow conspecific social interactions (e.g., schooling in fish species).

• provide a balanced, stable environment that supports the animal’s physiologic needs.

• provide the appropriate water quality and characteristics, and permit monitoring, filling, refilling, and changing of water.

• allow access to adequate food and removal of food waste.

• restrict escape or accidental entrapment of animals or their appendages.

• are free of sharp edges and/or projections that could cause injury.

• allow for observation of the animals with minimal disturbance.

• are constructed of nontoxic materials that do not leach toxicants or chemicals into the aquatic environment.

• do not present electrical hazards directly or indirectly.

Environmental enrichment strategies for many aquatic species are not well established. The implications of a barren versus an enriched environment on well-being, general research, growth, and development are unknown or poorly defined, as is true of individual versus group (social)