A more complete view is possible using fluorescent microscopy. This can directly determine populations of micro‐organisms, including a wider variety of bacteria as well as viruses. To determine the types of micro‐organisms, DNA analysis is required (microbiomics). This involves extracting, amplifying, and sequencing genomic DNA. Microbiome analyses have been reported for closed aquarium systems and have shown changes in bacterial diversity and evenness following routine maintenance such as water changes (Van Bonn et al. 2015; Patin et al. 2018). Further information and resources are available at the Aquarium Microbiome Project (www.aquariummicrobiomeproject.org).
Water Quality Testing Options
There are a wide variety of test methods available; a description of a possible water quality testing kit for fish veterinarians is provided in Box A2.2. Commercial test kits are available from various distributors (e.g. API, CHEMetrics, Hach, Seachem, Tetra). Handheld or system‐mounted meters are available from various commercial suppliers (e.g. Fisher Scientific, Hach, LaMotte, Oxyguard International, Pentair, YSI Inc.). Some methods, such as spectrophotometry, high‐performance liquid chromatography, and ion‐exchange chromatography may be limited to zoo and aquarium laboratories, and commercial, state, or federal aquatic animal health laboratories; the assays may be available to the public.
Factors to consider when selecting water quality test methods include accuracy, sensitivity (detection limits), calibration and maintenance requirements, ease of use, cost of purchase and maintenance, durability, reliability in working conditions, and associated disposal requirements (e.g. reagents).
When building a water quality testing program for an institution or practice, it is helpful to start with target ranges for each of the systems (based on the needs of the species and the life support equipment used), the expected ranges for the source water, and targets for disposal of the discharge water. This can be followed by a risk assessment of the most likely issues:
Source water (e.g. low dissolved oxygen, inappropriate temperature, incorrect composition of salt mixes, high chlorines in municipal water, high iron in well water).
System water (e.g. high nitrogenous wastes, pH change in low‐pH systems, temperature change in tropical fish systems, oxidative by‐products and low iodide in systems with ozone disinfection, drug assays). It may be useful to divide systems based on age (e.g. newly established/newly stocked versus stable) or use (e.g. quarantine systems).Box A2.2 Minimum Water Quality Testing KitThermometer for temperatureRefractometer or conductivity meter for salinityColorimetric tests for ammonia, nitrite, nitrate, alkalinity, copper, chlorine, +/‐ calcium, phosphate, iodidepH meterDissolved oxygen meter+/− Total gas pressure meter
Discharge water (e.g. drug residues, temperature, salinity, pathogen load).
Transport water (e.g. low dissolved oxygen, high ammonia, inappropriate temperature).
Consideration can also be given to potential research topics. These analyses can be used to guide decisions on type of testing, frequency of testing, and hardware, space, and staffing requirements.
Conclusion
Water quality parameters are more complicated than this chapter might suggest, but in general, acute changes should be avoided, and long‐term monitoring should be used to identify gradual changes. Parameters should meet the needs of all the animals and vascular plants or algae in the system and allow for seasonal changes that match the natural history of the species. The goal is to create balanced systems that show resilience.
Additional details are available in a number of excellent references, including Mohan and Aiken 2004; Noga 2010; Stamper and Semmen 2012a, b; Baird et al. 2017.
References
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