In fish farming, water is a very important medium for fish survival. Meanwhile, frequent rains in the rainy season can threaten the survival of aquaculture fish because it can trigger a high number of pests and disease-causing microorganisms in fish. This occurs due to frequent fluctuations in water quality parameters.

• Rainwater that falls has a high level of acidity or pH, so that aquaculture ponds exposed to rain will experience an increase in acidity or pH to 5-6 even though the optimal pH for cultured fish is between 7-8.
• Then in the rainy season, low temperatures also affect the decrease in the temperature of aquaculture ponds, even though the optimal temperature of fish is around 25-30 °C, but in the rainy season the temperature can be below 24 °C.
• Furthermore, in the rainy season usually sunlight does not reach the pond, this can cause the Phytoplankton in the pond to die so that there is no supply of oxygen in the pond and dissolved oxygen in the pond is reduced. Good dissolved oxygen in cultured fish is 3-5 mg/L. In the rainy season dissolved oxygen can be below 3 mg/L, and usually when the fish lacks oxygen it can be indicated by the appearance of the fish to the surface while its mouth is taking the air.
• Mass mortality in Phytoplankton can lead to an increase in ammonia because Phytoplankton itself is an organism that decomposes residual ammonia from feces and feeds in ponds, so that the ammonia in the pond will increase in large quantities and this will be toxic to cultured fish.

Significant fluctuations in water quality parameters can cause aquaculture fish to become stressed so that fish are very susceptible to disease and can even directly cause mass death and this is not expected by cultivators, for this reason it is necessary to control water quality parameters frequently, especially when it rains for a long time. The solutions that cultivators can do if there is a change in the water quality parameters above include:

• If there is a decrease in pH, agricultural lime can be added to increase the pH of the pond water.
• If the temperature decreases, the pond can be added with reservoir water (water that has been left for several days) until the temperature becomes normal. Even for some types of cultivation in the hatchery process, it is not uncommon to provide water heaters in the hatchery pond, this is taken so that the fish or cultivated animals do not die.
• If dissolved oxygen is reduced due to prolonged rain, the oxygen supply or aerator must be increased, there are even some cultivators who cultivate in a very large pond, so they add an aerator so that oxygen can be supplied properly.
• The increase in ammonia in water due to the rainy season can be treated such as limiting the quantity of feeding, also by changing the water but not replacing the entire water medium, the water replaced should not be more than 30% of the total pond water, because if there are too many fish will be stressed due to changes significant water quality.