Diagnosing Disease Problems
Monitoring your fish and aquarium is the most important part of early identification and management of disease problems. Since the fishes cannot simply tell us that they are feeling sick or uncomfortable we must educate ourselves as to their normal and abnormal behaviour so that we can have a functioning ‘early warning system’ before the majority of the population becomes affected. In captivity, rainbowfishes frequently exhibit behaviour which may be described as abnormal because they are not known to be a feature of the natural/wild behaviour of the species, or because they appear inappropriate in time or frequency of performance. Under suitable aquarium conditions, healthy rainbowfishes display “normal” behaviour. As aquarium hobbyists, we should become familiar with the normal behaviour of our fish.
Changes in behaviour may vary considerably, from stress due to their housing conditions—or the nature of captivity itself—but some of them are symptoms of specific diseases. These symptoms may include reduced or cessation of feeding, lethargy, floating near the water surface and/or swimming in an oblique position with the head directed toward the surface. Increased or laboured respiration (as indicated by “gasping”, flaring of opercula or rapid opercula movement) and breathing at the surface. Staying relatively still in one place in the aquarium, often accompanied by shimmering or shaking.
Flashing—every now and then an individual will swim towards the bottom and then suddenly move forward, turning on one side and appearing to rub one flank on the substrate or some other object. Fish will often injure themselves when they do their “flashing” against sharp rocks or other objects, and will often lose scales in the process. Generally this is a sign of ectoparasite infestation. Usually the fish will flash repetitively as opposed to just once. Poor water quality can also be the cause of flashing behaviour.
Physical chances may also become apparent, such as abnormal growths, lesions, loss of some scales and cloudiness of eyes. Fins may become tattered or eroded. The gills may become pale; clogged with mucus and the filaments may appear swollen or fused together. Change of body colour that does not match expected changes due to maturity, courtship or reproduction. This may involve a fish becoming dark in colour or lost of colour, with decreasing intensity over the entire body.
Most of these behaviours are difficult to assess based on a quick glimpse of the individual fish in the aquarium, and it is only the accustomed eye of the experienced aquarist that can detect them. The clinical signs of fish disease that can be directly observed by the eye are generally quite indicative of the disease group. However, fish diseases often have clinical signs that can be easily mistaken for a number of diseases. Visible examination of the skin and gill tissue may be sufficient to detect the presence of common parasitic infections (some fungi, protozoans and metazoans). However, identification of many pathogens, especially bacteria, requires the skill of a specialist using specialised analytical techniques.
If one is certain that a problem exists the next step is to determine if the problem is related to environmental or biological factors. Any time you observe a problem with your fish; always check the temperature, pH, ammonia and other water parameters. Far more rainbowfishes die from inappropriate aquarium conditions than disease. Water quality problems may be alleviated by dilution or changing with fresh water. Quite often, a simple water change will result in the recovery of the fish. However, treatment of infected fish with a therapeutic drug or chemical may ultimately be necessary. If treatment is indicated, it will be most successful if it is implemented early in the course of the disease while the fish are still in good condition.