Dissolved oxygen meters are quick and convenient to use, but expensive and require regular maintenance to function correctly. Colorimetric samplers or kits are reasonably accurate and suitable for field analyses, but sometimes difficult to interpret at night with limited light. If multiple readings are frequently taken, a polarographic meter is the preferred method. One possible exception is a computer monitored, intensive recirculating system. A variety of moderately priced colorimetric kits are available to monitor ammonia and niaite.
Greatest precision is obtained with a spectrophotometer.
Meters are available over a wide range of prices. Performance depends upon daily calibration and regular maintenance. Calibration is done with known standards called buffers. Colorimetric tests lack the precision of a meter, but are quick, economical, and adequate for field analyses. Conductivity meters are widely available and relatively inexpensive.