Bacteria are not so affected by salt if the saline concentration is very low. Wind, Rain and Water Change Weather conditions such as wind and rain can quickly change how much salt there is in a pond or water feature. Rain adds water to the pond and reduces the percentage of salt in the water. Use one of the many kinds of test kits available for determining the salinity of the water. Then add more salt to the water to restore it to the proper saline level.
Wind causes the pond water to evaporate, increasing the percentage of salt in the water.
Again, the proper method is to test the salinity of the water, and then add more water until the proper saline level is reached. If you do a water change, you also change the amount of salt in the pond. Salt is evenly distributed in the pond, so when you perform a water change you must proportionally return the salt to the pond. Determine how much new water you added to the pond, and then add enough salt to cause that new water to reach the proper salinity level. In a salt dip treatment, the injured or sick fish are exposed to a strong saline solution for short period of time, say up to 30 seconds or a minute.