Quarantine is a key issue when dealing with ornamental fish. The rapid spread of pathogens through the water alongside a less advanced immune system (compared to mammals) makes a correct “biosecurity plan” mandatory.
Icthyopathology, the study of fish diseases, is a growing area with a wide range of job opportunities but is often disregarded by veterinarians. In fish, most pathologies appear due to poor management of water quality, lack of quarantine and preventive treatments, poor nutrition, and incompatibility between tankmates. Knowledge of fish diseases comes mostly from aquaculture and the number of drugs with proven efficacy is very small, with even fewer drugs authorised for use in fish. The great diversity of ornamental fish species makes the work even harder. We could say that a surgeonfish and a shark are as similar as a cow and a dog (differences in diet, the anatomy of the digestive system,…). The key to a healthy aquarium includes adequate water quality, proper nutrition, and preventive healthcare.
The mortality pattern is key information when working with fish. It can help us discern whether it is an infectious disease, water intoxication or pathology affecting only one or a few individuals. Mass mortality appears when a toxic product poisons water, most commonly ammonia and nitrates. Daily mortality of several fish in a period of time (“drip mortality”) happens when an infectious agent is present. In that case, we must consider the tank as a “diseased aquarium”. The mortality of a few individuals could be the consequence of aggression by tankmates or husbandry-related problems.
Drug administration in small fish, shoals, and “diseased aquariums” is frequently done through bath treatments. This can be performed in two ways: long-term bath or short-term bath. The first one involves dissolving the drug in the aquarium according to the dose and periodicity indicated. We must ensure water quality, temperature, and oxygenation while the aquarium is under treatment. The latter consists of dissolving the drug in a container with water from the aquarium, with the fish returning to the tank after the treatment. An air diffuser must be fitted to maintain the oxygen level in the container in order to avoid oxygen depletion.