Continued…
Prevention of Nutritional Disorders.
These problems occur due to improper feeding of fish, but can also be related to fish health or the environment. In most cases, this can be avoided. Nutritional disorders often take a long time to manifest – usually measured in weeks or months rather than days, and symptoms can be vague. Sometimes irreversible physiological changes occur even before the aquarist suspects a problem. Liver damage, however, affects the overall health and growth of the fish and is potentially life-threatening. The main principle to follow is proper feeding of the fish.
Diseases caused by improper nutrition can result from feeding monotonous or spoiled food. Digestive disorders manifest as inflammation of the stomach and intestines (mucous excrement, increased body cavity, lifting scales, etc.). Monotonous food lacking certain vitamins leads to avitaminosis, undermining the health of the fish. The problem is that fish should be fed suitable food in the right quantity and frequency. Observation is very important – no fish should suffer from obesity or, conversely, from exhaustion. If this occurs, it should be identified and eradicated at the earliest stage. Many aquarists do not realize that their fish are gaining weight gradually as a result of the slow progression of this condition. When fish are purchased, they are rarely obese.
Very cheap aquarium fish foods, as well as foods intended for fish production (where the main goal is intensive fish growth rather than a long life), may also contain 
unsuitable fats and should be avoided. The reason lies in the long-term consumption of inappropriate dietary fats (high-saturated fats). Such fats are not easily digested and accumulate in the liver. Aquarium fish, like many other pets, are usually too overweight.
Obesity in fish can lead to swimming difficulties. In addition, it is accompanied by invisible internal problems – such as fatty liver, digestive tract disorders, and functional infertility resulting from fat deposits around the gonads. Signs include an abnormally large body girth, especially in the belly area. In some fish, obesity can cover the entire area between the abdomen and the head. Do not forget that females can increase in girth, often quite significantly, when their bellies fill with ripening eggs.
Unlike obesity, undernutrition is rarely seen in the home aquarium, although it can sometimes be observed in recently imported fish. Signs include a gradually decreasing body girth, ultimately emaciation and a sunken belly; lethargy. However, certain diseases, such as fish tuberculosis, can also cause these signs. This happens when fish are fed inappropriate food, or the amount is insufficient, or it is offered at a time when the fish are inactive – for example, when keeping nocturnal fish in the aquarium and feeding them only during the day.
Loss of appetite due to environmental problems (including stress and other diseases), as well as the inability of fish to compete effectively for food with tank mates, can also be a cause. Proper nutrition combined with regular monitoring of food intake and feeding behavior makes this easy to manage. A caring aquarist should notice in time that their fish are not eating properly and take necessary measures to correct the situation before signs of emaciation appear.
Long-term feeding with poorly balanced food or food deficient in vitamins, especially if the diet is monotonous. Some cheap fish foods may lack specific vitamins. Some vitamins (B-complex vitamins, vitamin C) are water-soluble and can leach out of dry foods into the aquarium water, and the extent of this problem varies depending on the food brand. Vitamin C can also degrade in dry foods during storage. Because of this, as well as the water solubility of this vitamin, it is the most likely to be deficient in fish fed such diets.
High-quality dry foods contain all necessary vitamins. However, the fish diet should be varied – this is a sensible precaution against vitamin deficiencies and many other nutritional problems. Fish suffering from a protein deficiency grow very poorly. Dry foods should be stored in airtight containers in a cool, dry place to prevent vitamin degradation and other spoilage. Once opened, dry food packaging has a maximum shelf life of two to three months. Rancid food can lead to muscle atrophy and nekronephrosis. Antioxidants must be added to commercial dry foods to prevent rancidity.
Gastrointestinal inflammation – this disease is predominantly typical of adult fish fed a monotonous diet, especially concentrated food. Causes include: long-term feeding on monotonous food (especially dry food) and feeding on poorly washed tubifex and bloodworms, Artemia along with shells and eggs, and marine krill, which has sharp spines and spikes that can injure the intestines of freshwater fish. Dry foods are difficult to digest and cause inflammation of the gastrointestinal mucosa. Freshwater fish must not be fed frozen krill. The disease Ichthyophonus can also be transmitted through it. Inflammation is also caused by incompletely thawed food swallowed by fish. The release of long thread-like excrement in fish is a consequence of chronic overfeeding leading to acute constipation.
Internal organ obesity – causes include: heavy multi-meal feeding of fish with the same food, abuse of dry foods. If the fat content of food for herbivorous fish exceeds 3%, and for carnivorous fish 5%, this 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.
Diseases associated with improper feeding. These diseases are usually caused by monotonous, inadequate, very fatty, high-carbohydrate, protein-deficient, vitamin-deficient, and mineral-deficient diets when feeding fish. Poisoning by bloodworms, intestinal inflammation from tubifex or frozen food are possible. Many parasites use animals eaten by fish as intermediate hosts.
Prevention of Stress-Related Diseases.
Stress is a serious problem for aquarium fish. Chronic stress usually ends in death eventually – for example, from slow exhaustion or lowered immunity and, consequently, increased vulnerability to infections. Unfortunately, its impact is often underestimated or attributed to other causes (for example, some imaginary infectious disease).
Stress is undoubtedly an integral part of fish life in nature. In particular, the fear of predators can serve as a prime example of natural stressors. However, within the tight confines of an aquarium, numerous stressful situations frequently arise that either do not occur in nature at all or from which fish can easily escape by swimming away to another place with more favorable conditions.
Signs of stress are numerous and non-specific, so diagnosis is most often made based on circumstances, i.e., a known potential cause of stress – for example, when a fish is bullied by other fish or the water contains a high amount of nitrates. These signs may include: • loss of appetite and, ultimately, progressively developing emaciation; • tendency to hide, including standing in the corners of the aquarium head up or down; • nervousness and panic-proneness (jumping, looking for a way to escape through the aquarium glass); • abnormal coloration (usually much darker, and sometimes paler than normal); • rapid breathing.
Causes include: • unfavorable environmental factors – unsuitable water chemistry; • poor water quality; • inappropriate temperature; • inadequate hiding places or an insufficient number of them; • aggression from other fish or fear of aggression from larger or more boisterous tank mates (even if they are actually peaceful and harmless fish); • external stimuli – for example, tapping on the aquarium glass; • constant or unusual activity near the aquarium, • loud noise and associated vibration.
In addition, diseases themselves can be stressors, as can certain medications and the treatment process itself. Aquarium maintenance (unless performed cautiously and calmly) can also stress fish. Constant changes in aquascaping, even with the best of intentions. Handling a fish, especially when catching it with a net, bagging, or transporting it, is always a source of stress. Even reproduction can cause stress in many fish. Chasing (which is sometimes part of the courtship ritual) can become a source of stress because the fish has no way to escape from a persistent but unwanted suitor within the tight boundaries of the aquarium. Fish of species that care for their offspring may perceive their tank mates, usually quite acceptable otherwise, as a terrible threat to their brood during spawning and experience stress because of it (while causing stress to other fish).
It is probably impossible to completely avoid any stress in aquarium fish. However, every effort should be made to provide them with as stress-free an environment as possible by creating suitable living conditions. This requires properly adjusting water chemical and physical parameters, decor, tank mates, nutrition, etc. External causes of stress resulting from human activity should also be minimized. The aquarist must remain constantly vigilant, regularly and carefully observing their fish and looking for any signs of stress or its potential causes.
Prevention of Wound-Related Diseases.
These are various injuries during fish transfer, sharp corners on objects in the aquarium, falling or careless rearrangement of interior decor and equipment, and aggressive fights among the fish themselves. External injuries include puncture wounds, abrasions, lost scales, frayed or split fins, loss of an eye, gill damage, etc. Some of these are minor, while others are more serious and can even be life-threatening.
Catching and transporting fish often causes damage, wounds, torn fins, and scraped scales. Newly introduced fish are frequently attacked by established residents. Fish can be injured by aggressive individuals during fights or mating rituals. The results are severe bites, abrasions, etc. Burns caused by contact with heaters also fall into this general category.
Cases of fish jumping out of an uncovered aquarium or out of the net during catching and transferring are not uncommon. In the process, they sometimes sustain injuries invisible to the observer, which can lead to fish death or the production of poor-quality offspring. Wounds appear from attacks by fish predators (hydras, leeches, dragonfly larvae, etc.), ectoparasites (Argulus, Lernaea, Piscicola, Dactylogyrus, Gyrodactylus, etc. – agents of parasitic diseases). Since the protective slime coat is damaged in the process, the wounded fish easily contracts various infections or fungal attacks.
Unsuitable decorative items can lead to minor injuries with potentially serious consequences. For example, rough substrate can abrade the mouths or gills of fish that dig in the substrate or sift it through their gills. Similar damage can be caused by substrate on the bellies or barbels of bottom-dwelling fish. Even a minor collision with very rough or sharp rocks (and other decor) can inflict a serious wound on a fish. Unstable decorative items can collapse and crush tank inhabitants. Fish can accidentally get stuck in some attractive opening – for example, filter intakes, flower pots, hollows in driftwood, or gaps between rocks, etc.
Different fish species tolerate injuries differently. Bottom-dwelling fish, accustomed to constant contact with rocks and sand, are insensitive to mucosal damage, while pelagic fish react very painfully to mucosal damage. In addition, different species have different wound-healing abilities. If a fish has good stamina and infection does not develop, even severe bites will be tolerated well. Weak and sick fish can fall victim to the most minor injury. Such injuries are most dangerous for larvae and fry.
Fresh injuries are easy to spot. These are damages to the slime coat, scales, fins, subcutaneous tissues, and even muscles. Burns can sometimes be difficult to distinguish from other wounds or skin infections. However, if a fish has a habit of lying on or under the heater, a burn should be suspected if an unexplained wound appears. Since the skin helps maintain the fish’s internal physiological salt balance, any extensive (или localized but serious) skin damage can lead to osmotic stress. In addition, even minor external wounds can become infected. If the injury is large, the fish cannot be saved. Damaged fins and tissues are capable of self-healing.
However, in unsanitary conditions, fungi and putrefactive microflora settle in the damaged areas. If this problem is not addressed directly, they can lead to death or permanent disfigurement of the fish. Internal injuries sometimes manifest as unusual behavior observed in combination with a known cause of injury. For example, damage to the swim bladder resulting from an attack (ramming) by another fish may manifest as a loss of buoyancy.
Most injuries are caused by aggressive behavior from other fish – either directly (e.g., bites) or when a fleeing fish collides with decor or equipment. Panic (e.g., if a fish is startled by outside activity) can also lead to injuries from collisions with objects. The same can happen when a fish darts around the aquarium or scratches against decor in the event of parasite infestation or disease caused by unfavorable environmental conditions. Large parasites can also directly injure fish at the attachment site. They form a small wound that can become infected, especially after the parasite detaches.
Wounds can be prevented by exercising common sense when selecting fish, decor, equipment, etc. However, the risk of aggression from some individuals against others always remains if two or more fish are kept together in the aquarium. Studying fish behavior often reveals their specific self-destructive tendencies (jumping, getting stuck in holes, lying on heaters). This allows appropriate precautionary measures to be taken. If you keep fish prone to burns, consider using a heating mat placed under the aquarium or a protective guard fitted over the heater tube. Providing fish with suitable hiding places will also help protect them from injuries.
To prevent mechanical injuries in fish, avoid injuring them during various procedures, remove particularly pugnacious fish from the aquarium, regulate the number of males (especially certain species of labyrinth fish and Cichlidae), be sure to cover the aquarium with a glass lid, carefully sort live food to remove fish predators, prevent fish ectoparasites from entering the aquarium, and do not place sharp objects (rocks, gravel, etc.) in the aquarium.
