the less intense the light.
Results of UVB application to aquatic systems have been mixed. Three 160‐W UVB heat lamps (T‐Rex® Active UV Heat) placed 91 cm above the water surface produced a UVB intensity of 0.1 ± 0.05 mJ/cm2 or mWs/cm2 but only over a surface area of 3.8 cm diameter directly below each lamp, despite observing a larger light footprint. A 50% variation in UVB intensity was also observed between each bulb. Additionally, light intensity degraded rapidly within the normal six‐month replacement cycle (Purgley et al. 2009). A similar study involved a Mega‐Ray® 275 watt Self‐Ballasted Flood UVB Lamp placed 61 cm above a tank with a diameter of 305 cm and depth of 183 cm. This produced a UVB intensity ~0.015–0.050 mJ/cm2 over a quarter of the tank and caused dermatitis in fish cohabitating with sea turtles after eight hours of exposure (Boylan pers. comm.).
A critical aspect of light is photoperiod. At a minimum, fish should be exposed to relatively steady photoperiods without sudden changes. This can be difficult in display aquaria where there is often demand for exhibit lighting during evening events. And to mimic natural diurnal cycles and prevent startling, periods of lower intensity at the start and end of the light period should be used to mimic dawn and dusk. Ideally, photoperiod should mimic natural seasonal changes for the species. Species‐appropriate light refuges should be provided to allow inhabitants choice.
Other Life Support Equipment
Some other life support equipment may be found on aquarium systems or to treat incoming water.
Ion‐exchange filters are deionization units that can be used to treat incoming freshwater. These use two types of synthetic resins to remove positively charged ions (cations) such as calcium, magnesium, and sodium, and negatively charged ions (anions) such as chloride, sulfate, and bicarbonate. In addition to conventional deionization, ion‐exchange filters can contain resins or adsorbent media that are selective for specific contaminants such as silica, ammonia, phosphate, nitrate, and heavy metals. Many have color indicators that change color as the resins become exhausted. Products suitable for aquarium use are preferable as they have very low levels of toxic leachables. Some freshwater resins can be regenerated using warm salt water. Some saltwater resins can be regenerated on site, but they typically require strong acids or strong bases to do so and the hazardous chemical handling usually makes ion‐exchange filtration impractical in saltwater systems. Expended resins should be discarded through appropriate hazardous waste. These differ from conventional ion‐exchange water softeners, which produce high levels of sodium or potassium and are not designed for fish systems.
Reverse osmosis systems can remove ions from incoming freshwater. They use a semipermeable membrane to remove 90–99% of impurities such as chlorines, chloramines, nitrates, phosphates, pesticides, and heavy metals. Reverse osmosis does not remove as much as deionization, but in practical terms the resultant freshwater is similar for both processes. Deionized or reverse osmosis water may be used in systems containing fish that prefer soft, low‐pH water and in the cleaning of sensitive equipment.
Carbon dioxide (CO2) scrubbers, injectors, or reactors can remove or add CO2. These may be found on high‐density aquaculture systems and low‐pH fish systems. Carbon dioxide is produced through respiration. The amount of CO2 in aquarium water affects the pH and alkalinity, since it becomes carbonic acid when dissolved in water. Too much carbonic acid lowers system pH, while too little increases pH.
If CO2 is too high, it can be addressed with increased aeration (e.g. air diffusers, packed column aerators), addition of calcium hydroxide or sodium hydroxide solution, or use of a CO2 scrubber. This is a device installed on the ambient air intake of an aeration device (e.g. air blower or foam fractionator) that contains an oxide or hydroxide media that absorbs CO2 from the air before it is drawn into the system. A color indicator is used to determine when the media is exhausted. The media is not usually considered hazardous waste, but it can be exhausted rather quickly, which can become costly to manage on larger systems.
If CO2 is too low, CO2 injectors or reactors can be used to supplement CO2 into the system. An injector typically uses a fine‐bubble diffuser to dissolve CO2 directly into the water from a pressurized source such as a cylinder or dewar (vacuum flask). A reactor pre‐dissolves the pressurized gas into the system water in a reaction vessel outside of the aquarium. Both methods should use a CO2 controller with pH as the control parameter.
Calcium injectors can inject calcium directly into a system in the form of calcium hydroxide solution. These are typically found on systems that house hard corals. Calcium reactors supplement calcium by separating calcium ion from carbonic acid in calcium carbonate media (like aragonite). This is done by bubbling pressurized CO2 into it within a reaction vessel outside of the aquarium. Both methods should be pH‐controlled.
Pond Life Support
One of the biggest issues with outdoor ponds is phosphates and sunlight causing algal and bacterial blooms. These are particularly dangerous when the biological oxygen demand (BOD) is high (e.g. in a heavily stocked system or at night when photosynthesis is not active). In these situations, a bloom can lead to life‐threatening hypoxic events. These can be minimized using shade and by controlling phosphates and potentially nitrogen and iron levels. Phosphates and nitrogen build up through the introduction of food and other organics into the system. Input can be limited by regular removal of decaying matter (e.g. leaves), covering with nets in the fall, and only feeding to appetite. In the system, they can be managed with chemical flocculation (e.g. precipitation with lime, lanthanum chloride, aluminum sulfate, or iron salts). Metallic flocculants work well, but some (e.g. lanthanum salts) produce flocs that must be prevented from entering the pond as they can disrupt gill function in fish. Aluminum sulfate is one of the most commonly used, but care should be taken when applying as it will decrease pH.
Coral Reef Life Support
Compared to fish‐only marine aquariums, coral reef aquariums require more intense lighting of the correct spectrum, turbulent water movement, and more stable water chemistry. Biological filtration for reef aquariums usually comes from the use of live rock from around existing reefs or from aquaculture. Foam fractionation and deep sand beds are also often used. Calcium injectors and reactors are often used to maintain proper pH, alkalinity, and calcium and magnesium levels that are critical for stony corals to maintain their calcium carbonate skeletons. Dedicated computers with electronic water quality monitoring capabilities may be used to control water chemistry parameters in complex systems.
Conclusion
In nature, aquatic organisms are an integral part of the natural environment that sustains them. Aquariology is the science of doing the best we can to model the environmental parameters needed for the species we have selected to keep in artificial environments. We cannot duplicate all of the natural processes that govern the ecological parameters that support the life of our animals in nature, but we should always endeavor to provide the best care we can.
For further reading, see studies by Carlson (1999), Overby (2002), Spotte (1991), Van der Toorn (1987), and Watson and Hill (2006), and the website of the Aquatic Animal Life Support Operators (http://aalso.org).
References
1 Aas, E. and Højerslev, N.K. (1999). Analysis of underwater radiance observations: apparent optical properties and analytic functions describing the angular radiance distribution. Journal of Geophysical Research 104: 8015–8024.
2 Adey, W.H. and Loveland, K. (2011). Dynamic Aquaria: Building Living Ecosystems. Amsterdam: Elsevier, Inc.
3 Anderson, P.A., Berzins, I.K., Fogarty, F. et al. (2011). Sound, stress, and seahorses: the consequences of a noisy environment to animal health. Aquaculture 311: 129–138.
4 Burns, A.S., Padilla,