The diseases of Aquarium fish from marine, cold and tropical waters species, are as complicated as those from human beings. Very little research has been done on the aquarium fish diseases by dedicated ornamental fish culturists, veterinary scientists, or fish-health professionals except by a few fish enthusiasts or hobbyists who happened to be doctors from the medical profession.
Fortunately, during the last few years, there has been an increase in countries like Norway, Greece, Chile, Canada, UK, Denmark, Austria, Sweden, Finland, Korea, USA, and Iceland. They have extensive investments in the aquaculture industries with an emphasis on food fish farming in controlled waterways and marine cages and pens. Diseases in caged fish are more prevalent than in the open sea. Therefore, for the food fish farmers, lack of positive control over health and diet problems from fry to adult stages of their fish will result in delayed harvesting and thus lower profits or even loss of income. The food fish rearing projects and hatcheries are hundreds of times more than those of the ornamental fish industries.
Let us hope that we will soon be able to benefit from these food-fish farmers’ research in fish diseases as they started to breed food fish from eggs to adult fish the way we breed our aquarium fish. We must remember that poor or inadequate environmental conditions induce stress and cause ill health and most disease problems.
The following are the main causes of fish diseases in aquarium fish:
Poor water quality, incorrect pH level, wrong water temperature, unsuitable water hardness, impurities in the water, and salinity (too much salt in a freshwater aquarium or too little in a marine aquarium).
High ammonia, nitrate, nitrite levels, and unsanitary conditions in the tank.
Too high in stocking levels and problems in fish compatibility.
Too much or too little aeration, insufficient oxygen in water, or too much carbon dioxide.
Improper diet and feeding regime. Fish are fed with the wrong type of diet or the top feeders are given food that sinks to the bottom. Overfeeding – too much uneaten food causes fouling and pollution of the aquarium.
The recent introduction of new fish or plants may introduce new parasites and diseases. Proper quarantine systems are required to introduce new fish or plants into the aquarium without introducing new problems.
Too many decaying plants or food causes bacterial bloom, and hence low oxygen content in water.
Organic waste and toxic substances such as an overdose or incorrect usage of antibiotics, nitrofurans, copper sulfate, formaldehyde, parasiticides, disinfectants, and even the common insecticide spray.
Improper maintenance or setting up of aquarium or pond such as the wrong type of water filtering systems and gravel are used.
Unnecessary transportation or rough handling of fish causes stress and external injuries. Any item from the above causes diseases in most aquarium fishes. The hobbyist should remember that there are plenty of pathogenic bacteria, parasites, fungi, etc. waiting to invade and attack your fishes the moment their immunological defense systems are not up to par.