This section is from the book "The Goldfish And Its Systematic Culture With A View To Profit", by Hugo Mulertt. Also available from Amazon: The goldfish and its systematic culture.
The goldfish, when in perfect health, carries the dorsal fin in an erect position, in other words, fully expanded. Its colors are very-distinct, the body of the fish glistening as though highly polished. The fins appear very clear, translucent, allowing an examination of their structure, they are also very flexible moving in the water with animation and grace. When closed by the fish, the gill covers fit tightly against the head.
Liveliness is not always an indication of good health, and, on the contrary, sluggishness is no positive evidence that the fish is ill.
But when the brilliant red color fades away into an off-colored pink, or the milky white portions of the body become intermixed with bloody streaks, or the fins of the fish appear to be coated with something unusual, or seem inflamed and stick together, or are carried close to the body, or when the gill covers appear so swollen that they will not fit tightly in their proper place, then the health of the fish has failed, and danger is close at hand.
Most of the diseases of the goldfish are the direct result of ill. treatment while kept in captivity, and nearly always originate in the breathing apparatus; the gills, when affected, fail to supply the blood with oxygen. Some of the diseases, to which the fish are subject, originate from improper methods of feeding, and always manifest themselves in disturbances of the stomach, and other digestive organs.
Again there are diseases that make their appearance periodically, the origin of which is involved in as much obscurity as that called "pink-eye," which attacks horses, and of which all have heard more or less.
This affection is the one most commonly met with. The fish become weak, the colors fade away rapidly, the appetite is lost, and the fish finally die if the disease is permitted to run its course without hinderance
The cause of the disease may be looked for in the interrupted functions of the gills. These organs become inflamed by the irritat-ting and poisonous gases that may exist in the water, or by the sudden changes of temperature in the same.
If the disease has not already advanced too far, the ailing individual or individuals, should be taken from the collection, placed in a vessel containing a sufficient quantity of water, and in which a number of flourishing aquatic plants are growing.
An even teaspoonful of common salt is then dissolved in the water, the whole then put in a light, well ventilated place, and kept at a temperature between 700 and 8o° F. During the first few days no food is necessary, and should not be given, after which the feeding may be re-commenced, beginning with very small quantities, administered at a regular hour each day. As the fish brighten up, and approach convalescence, the quantity may gradually be brought up to the usual amount.
The first sign of the presence of this disease shows itself in the indifference manifested by the affected individual. They are seen swimming about in a careless, purposeless way, now and then stopping to make the vain attempt to remove something from their gills that annoys them. They are apparently coughing. Their appetite decreases. It is evident that the gills are out of order, they thus failing to take up oxygen for the blood.
As the disease progresses the fish becomes lean, as seen back of the head, on the back, and the sinking in of the abdomen, causing the head to appear too large and out of proportion. The gills become agglutinated which results in the destruction of their structure by decay. Having arrived at this stage the fish is too weak to balance itself and swims head downward, finally standing on it, because it is the heaviest part of its body, and dies in that position.
The duration of this disease varies in different individuals and seasons, it being of shorter duration during cold weather.
The origin of this disease may be traced back to unnatural treatment while in captivity, as fish in native waters never get it, and in well managed aquaria they very seldom have it, while in those badly managed they frequently die of this disease. The cause of the disease arises from invisible organisms called tubercular baccillae, these being inhaled by a fish whose breathing apparatus is in the least out of order, infest these organs and destroy them.
The disease proves fatal in all cases, or has invariably done so in the writer's experience, who has so far failed to discover an effective remedy. The disease may be avoided by keeping the aquarium in perfect condition.
This disease generally appears during the colder season of the year, seldom manifesting itself when the weather is warm or hot.
The body of the fish becomes coated with a layer of some whitish substance, the deposit beginning on the back near the head.
This white, slimy substance, when examined under a powerful microscope, reveals a number of parasites darting about hither and thither across the field of the instrument. These minute organic bodies, technically termed bacteriae, resemble a wood-tick in general shape. They appear to eat into the skin of the fish, destroying that structure, and in consequence interfere very much with the function the skin performs in throwing out poisonous substances that form in the tissues inside. The beautiful colors of the fish disappear from the tainted parts, they becoming quite black. The result of the disease is the death of the fish.
When afflicted with the trouble, the fish can be observed rubbing itself against the plants, the rocks, or in the sand upon the bottom of the aquarium.
The cause of the disease may be found in the usual over-feeding, in which case the remnants of food remain in the water until decomposition sets in. The temperature not being favorable for the production of water-purifying insects, the bacteriae make their appearance greatly to the detriment of the fish.