Which of the following statement about a good fish pond is true?

The statement that is true about a good fish pond is that "it must have low concentration of dissolved salts." Fish ponds need to maintain a certain level of salinity to support the health of fish, but if the concentration of dissolved salts is too high, it can be harmful or even fatal for the fish. High levels of dissolved salts can also affect the growth of aquatic plants and lead to an imbalanced ecosystem in the pond. Therefore, it is important to maintain a low concentration of dissolved salts in a fish pond to ensure the health and productivity of the fish.