Disease attack on cultured fish can be prevented if the culture environment where the fish live and develop is in a healthy condition. Proper preparation of the culture pond, which includes drying, liming and salting, can also prevent the occurrence of disease in fish. The environment where fish are kept can be the cause of fish disease. If the environment does not meet the standards recommended in good fish farming, the fish will be susceptible to disease. Generally, fish diseases will arise if the fish and the environment are not in balance.
Disease caused by the environment.
The environment as a place for fish maintenance cultivation media affects the problem of disease attacks. Generally, fish diseases caused by environmental factors cause considerable losses, because these deaths occur and last very briefly and generally kill the entire number of fish being kept. Diseases that kill the entire fish population usually occur due to turnover in the environment where fish are kept, and can also be caused by poisoning due to explosive plankton populations, poisoning from pesticides, industrial waste poisoning and other chemical poisoning.
A. Fish suffocation (oxygen depletion)
Characteristics:
Dissolved oxygen in pond water can decrease, generally this lack of dissolved oxygen occurs in aquaculture ponds and in public waters (floating net cages) especially in the morning. Oxygen deficiency in fish ponds that occur in the morning is due to the presence of a fairly high phytoplankton population, or when conditions of low atmospheric pressure, with less sunlight entering the pond for a long time.
1. Replace old water with new water.
2. Increase the oxygen content in the water through oxygen diffusion from the air to the water by moving the water flow such as the use of waterwheels, aeration and water pumps.
3. Increase the oxygen content in cultured water by injecting pure oxygen into the water.
4. Setting the stocking density of the fish being reared. Fish stocking density must be adjusted to the carrying capacity of the water in supplying oxygen.
B. Nitrite poisoning
Characteristics:
Nitrite poisoning (methemoglobinemia) also known as brown blood disease is a fish disease caused by high nitrite concentrations in fish ponds. The source of nitrite comes from residual protein metabolism, either from uneaten feed or fish waste.
Symptoms of methemoglobinemia or nitrite poisoning are that the fish will have difficulty breathing, the physical condition of the fish is weak, the fish often jumps to the surface of the pond water or the fish often gathers at the water intake channel, the color of the fish gills is brownish red.
1. To control fish diseases caused by nitrite poisoning, namely by increasing the oxygen content in the pond water.
2. Replace old water with new water to reduce the concentration of nitrite in the water.
3. Chloride is added to the water, usually with crossover salt, to increase the Cl:NO2 ratio (at least 5:1).
4. The amount of fish feed that is not eaten by the fish should be reduced.
5. Use of N-reducing probiotics (Nitrosomonas, Nitrobacter).