Diseases associated with improper and inadequate feeding.
These diseases are usually caused by monotonous, insufficient, very fatty, high-carbohydrate diets, protein deficiency, vitamin deficiency, and mineral deficiency when feeding fish. Other causes include bloodworm poisoning, and intestinal inflammation caused by tubifex worms or frozen food. Many parasites use animals consumed by fish as intermediate hosts. Rancid food can lead to muscular atrophy and necronephrosis.
The most characteristic symptoms of fish poisoning are cramps, twitching, impaired coordination, necrosis (destruction) of the gills, and paralysis. Food poisoning may also cause inflammation of the gastrointestinal tract and dropsy. A very important observation is that no fish should suffer from obesity or, conversely, from emaciation. If such a condition occurs, it must be identified and eradicated at the earliest stage.
Inadequate nutrition can lead to a sunken belly, while overfeeding or an inappropriate diet can, conversely, lead to obesity. This type of body shape distortion is perhaps the most common. Antioxidants must be added to commercial dry foods to prevent rancidity. Fish suffering from protein deficiency grow very poorly.
Loss of buoyancy or buoyancy control. As a rule, this is the result of swim bladder dysfunction. The fish may swim head or tail down, partially or completely on its side, or even belly up. This problem may indicate an injury or a bacterial infection of the swim bladder. In addition, swim bladder dysfunction occurs in the late stages of certain diseases (e.g., dropsy, fatty liver, general obesity). Lethargy in fish can indicate gastrointestinal inflammation or obesity.
If the fish is bloated. This occurs in the late stages of dropsy and obesity. Bloating caused by tapeworms is always unilateral and can cause the fish to swim on its side. An internal tumor, much like dropsy, causes scale protrusion, but only on one side. If the swelling develops slowly, it is either obesity or tapeworms. Sudden swelling is caused by pathogens.
Diseases caused by improper nutrition can be the result of feeding monotonous or spoiled food. Digestive disorders manifest as stomach and intestinal inflammation (mucous excrement, increased body cavity, raised scales, etc.). A monotonous diet lacking specific vitamins leads to avitaminosis, which undermines the fish’s health.
Reddened areas can be the result of damage caused by external parasites; injuries; irritation caused by acidosis, alkalosis, or ammonia; inflammation or hemorrhage resulting from a systemic bacterial or viral infection; or vitamin C deficiency.
Some fish have a deformed skeleton as a result of a genetic mutation. If the deformation is minor, it is not always noticeable. In addition, such deformation can occur as a result of injury; fish tuberculosis and certain other diseases caused by pathogens; infestation by certain types of external parasites; unfavorable water parameters (especially for young, growing fish); or vitamin deficiencies. A tumor can make the fish appear deformed (this phenomenon is relatively rare). Inadequate nutrition can lead to a sunken belly, while overfeeding or an inappropriate diet can, conversely, lead to obesity. This type of body shape distortion is perhaps the most common.
Deformities can also occur at an early stage of a fish’s development or later in life due to other causes. These causes include environmental problems, injury, fish tuberculosis, vitamin deficiency, and parasite infestation (e.g., nematodes). Such deformities should not be an obstacle to breeding. However, do not buy fish with any deformities, as there is no way of knowing how they acquired them.
Without going into detailed analysis, we can say that our water lacks many macro- and microelements, especially potassium, iron, magnesium, and manganese, while nitrogen and phosphorus compounds are present in excess, which is highly undesirable. This situation can be mitigated by regular water changes (to reduce the concentration of harmful substances) and adding the missing elements after each change. Aquarium water also typically requires forced oxygenation and carbon dioxide saturation.
A common mistake made by beginner aquarists is frequent and complete water changes in the aquarium. You should not frequently, and especially not completely, change the water in the aquarium. Meanwhile, for most tropical fish species, the water should only be refreshed, and no more often than once every 7-10 days. Generally, this procedure is necessary to reduce the amount of decomposition products and, most importantly, by changing the water, to reduce the concentration of end products of decomposition, namely nitrates. Water is the habitat for fish and plants, and regular water changes have a very beneficial effect on the condition of aquarium inhabitants. Fresh water introduces necessary doses of microelements for development, while old water removes a portion of the fish’s metabolic waste.
Special attention must be paid to partial water changes when the pH is 7.5. When changing a large amount of water (up to 0.5 of the volume) to fresh water with a pH above 7.0, a large amount of ammonia can form from ammonium, resulting in fish poisoning. A complete water change is an extreme measure and is performed in cases of contagious mass infections of fish, the appearance of parasitic microorganisms requiring subsequent disinfection, or severe substrate pollution.
Internal Organ Obesity.
Causes include: heavy, frequent feeding of fish with the same food, and overreliance on dry foods. If the fat content of food for herbivorous fish exceeds 3%, and for carnivorous fish exceeds 5%, it often leads to fish obesity. The disease is promoted by a lack or absence of aquatic vegetation. Such maintenance and feeding lead to metabolic disorders in fish. Fish become sensitive to the slightest changes in environmental conditions and more susceptible to invasion and infectious diseases.
Symptoms: Lethargy. Abdominal bloating. The front part of the belly increases significantly. Fins become frayed and very susceptible to bacteria and fungi. The disease is chronic and remains unnoticed in its initial stages. Fish do not lose their appetite, but become sluggish. The front part of the abdomen gradually enlarges. Sometimes body cavity dropsy is observed, expressed by an excessive enlargement of the abdomen. Liver degeneration occurs, leading to death. Upon dissection, the internal organs are covered in fat, and the blood is lighter in color. The disease generally ends in the death of the fish, as lipid metabolism disorders are irreversible.
Treatment: Switch to a fat-free diet and add vitamin B. Obese fish cannot be cured.
Feed Poisoning.
To avoid poisoning when feeding fish, do not use low-quality dry foods that have been stored for a long time. Rancid food can lead to muscular atrophy and necronephrosis. Antioxidants must be added to commercial dry foods to prevent rancidity. Dry food should be purchased with the expectation of using it within no more than 3 months and before the expiration date. Fish suffering from protein deficiency grow very poorly.
Poisoning can be caused by live food harvested from bodies of water polluted by industrial, municipal, and domestic wastewater. Many parasites use animals consumed by fish as intermediate hosts. There are cases of fish poisoning from live foods (daphnia, tubifex, bloodworms) harvested from water bodies contaminated with wastewater containing toxic substances. These organisms are capable of accumulating various toxic substances in their bodies at concentrations much higher than in the water. At the same time, toxic substances do not always cause the death of aquatic organisms (chironomid larvae, daphnia, cyclops, etc.), but instead accumulate within their bodies.
Rain and floodwaters can wash mineral fertilizers and pesticides used to combat crop pests, malaria mosquitoes, and other harmful insects into water bodies where live fish food is harvested. These chemicals also accumulate in aquatic organisms in higher concentrations than in the water. When fish are frequently fed such food, toxic substances accumulate in the fish’s body and cause poisoning, characterized by central nervous system dysfunction and often resulting in the death of the fish. Unlike warm-blooded animals, fish do not always exhibit gastrointestinal inflammation during poisoning.
Tubifex worms must be kept in clean water for 6-7 days before feeding, as they are harvested from heavily polluted water bodies.
The quality of the food and the probability of fish poisoning can be tested as follows: grind the internal organs of a dead fish or the food itself with granulated sugar and feed this mixture to houseflies kept in a glass jar covered with cheesecloth. If the flies die with typical signs of convulsions and paralysis, the live food contains toxic substances.
Avitaminosis and Hypervitaminosis.
Hypervitaminosis – possible when using artificial vitamin preparations in excessive doses. Such situations can occur when using industrial and medical products and aquarists calculate dosages themselves.
Avitaminosis – in acute form, usually the result of abundant and monotonous feeding or the use of medications. At the same time, one should not forget that even when explicit symptoms of avitaminosis are absent, the addition of special aquarium vitamin supplements significantly improves well-being, boosts immunity, and enhances the coloration of many fish and invertebrates. In addition, these preparations help them survive difficult situations associated with stress, reproduction, medication administration, etc.
Mineral and trace element deficiency: – deformation or absence of gill covers; – deformation or absence of fins; – curvature or deformation of the spine.
Avitaminoses. These deficiencies are more commonly observed in juvenile fish. Vitamin shortages are caused by prolonged feeding on monotonous, vitamin-poor foods or old, expired food in which vitamins have already degraded. Vitamin deficiency leads to loss of appetite and growth disorders. Apathetic, poor-looking fish are almost always an indicator of vitamin deficiency. Vitamin deficiency makes fish susceptible to diseases. In this case, even the slightest trigger (such as cleaning the aquarium or introducing new fish) is enough for a disease to develop.
Vitamin A deficiency: – Lightened coloration. Erosion and decay of the caudal fin. Clouding of the cornea. Exophthalmos (pop-eye). Low fertilization rate. Vitamin A promotes visual development and healthy growth. It is also very important for protecting mucous membranes and ensuring fertility. Vitamin A deficiency leads to eye damage and bleeding under the mucous membranes.
Vitamin B deficiency: – Underdeveloped gill covers. Cessation of feeding. Darkened coloration. Darting movements. Loss of balance. Convulsions. Abdominal bloating. Paralysis of the dorsal and pectoral fins. Hemorrhages around the nostrils and on the gill covers. Flaring of the gill covers. Vitamin B1 is needed to produce energy from carbohydrates and to supply the brain and nerves with sugar. Vitamin B1 deficiency leads to impaired mobility, convulsions, rapid breathing, and loss of balance. Vitamin B2 is essential for protein utilization, muscle recovery, and mucous membrane protection. Vitamin B2 deficiency leads to internal organ bleeding under the mucous membranes, emaciation, and nervous system dysfunction.
Vitamin B5 (vitamin PP) plays an important role in the synthesis of various enzymes. A typical sign of this vitamin deficiency is organ damage. Vitamin B6 is crucial for the nervous system. Deficiency leads to nervous system damage manifested by impaired mobility, hyper-excitability, refusal of food, and skin defects. Vitamin B12 is required for the digestive organs and for the regeneration of hemoglobin, which is necessary for oxygen transport. Vitamin B12 deficiency leads to a shortage of red blood cells, subsequently resulting in apathy and growth retardation.
Vitamin C deficiency: – Fin erosion. Skin tumors. Spinal curvature. Abnormal growth of gill covers. Tumors form on the skin near the caudal, ventral, and pectoral fins, which eventually resorb. Impaired formation of tendons and cartilage leads to spinal curvature or even fracture, and filamentous splitting of the cartilage of the gill filaments. Vitamin C is important for skeletal development. Furthermore, it plays a vital role in strengthening the body’s immune defenses. Vitamin C deficiency leads to scale deformation and makes fish susceptible to diseases. This vitamin is very sensitive to air, so foods contain long-lasting stabilized vitamin C.
Vitamin D deficiency: – Rachitic bone deformation. Spinal curvature. Underdevelopment of gill covers. Vitamin D regulates the absorption of calcium and phosphorus and is therefore crucial for skeletal growth. Vitamin D3 deficiency leads to bone deformation (rickets).
Vitamin E deficiency: – Reduced appetite. Complete cessation of growth. Exophthalmos. Vitamin E stimulates the formation of sex hormones. In addition, it regulates other vitamins in the feed, such as valuable fatty acids. Typical consequences of vitamin E deficiency are infertility and fatty liver.
Vitamin H (biotin) is a growth-promoting factor. Deficiency leads to growth disorders, as well as loss of appetite and convulsions.
Vitamin K promotes blood recovery after injury. Deficiency leads to poor wound healing and liver damage.
Choline is needed for fat digestion. Choline deficiency leads to fatty liver.
Treatment: To prevent these issues, feed the fish a complete diet combining dry and live foods with vitamin supplements, and include dandelion and lettuce leaves in the diet of herbivorous fish, along with vitamins from reputable manufacturers.
Fish feeding problems. What to do if…
How and what to feed fish during vacation? Weekend foods. 
