Environmental Toxicities

Fish have a very intimate relationship with their surrounding aquatic environment, surrendering them vulnerable to waterborne toxicities. Most aquarium fish live in a closed system (water has to be manually removed and added to be renewed), so the effects of such toxins can be cumulative and devastating. Rainbowfishes are less likely to encounter pesticide toxicities than their wild counterparts, but toxicities can still occur. Most household pesticides are highly toxic to fish.

Organophosphates, chlorinated hydrocarbons, pyrethrins, and pyrethroids make up the most likely suspects in pesticide toxicity cases. Indoor pest extermination most likely involves aerosol spraying procedures, so it is important to turn off air pumps and cover the tank until the danger of pesticide introduction has passed.

In general, few household toxicities present with pathognomonic symptoms. Clinical signs vary but are mostly neurologic in nature. Acute reactions include paralysis and death. Chronic exposure has been associated with poor growth and deformities in fry. Vertebral fractures have also been reported. In situations in which accidental contamination of the aquaria is suspected, the treatment is to move the fish to clean, uncontaminated water and to provide symptomatic therapy such as additional aeration, treatment of secondary infections, and reduction of stress. In cases in which the fish cannot be removed, frequent, ample waterchanges should be undertaken.