After being a fish keeper for years,(and working in a totally unrelated career) i went back to school for environmental science, and ended up as a chemist/microbiologist in a drinking water facility.
I realize this has no "direct" relationship to the fish themselves.
But it provided all the BAT (best available technology) for water testing (information, and equipment (everything from simple pH meters (and their calibration) to hi-tech spectrometers) filtration methods such as UV, ozone, fractionation, other new technology, and a lab to experiment in, many media types, yet seldom required field work.

Within the facility part of my job was to examine and access the efficiency of 32 olympic swimming pool sized bio-filters, test for pathogens, and the bacteria in bio-media.
All these did have a direct relationship toward my understanding of, and fish and one of the most important parts keeping.
