The color of the fish pond water is formed by the combination of dissolved substances, suspended particles, plankton, sky and color reflections at the bottom of the pool. Because various types of phytoplankton cells contain different pigments, when the species and amount of phytoplankton are different, the pool water will show different colors. Experienced fish farmers can judge the quality of water based on the color of the water. First, the yellow-green and refreshing water quality is moderate, and the composition of plankton is mainly diatoms. There are also many green algae and eutrophic algae. Second, grass green and refreshing The water quality is relatively strong, mainly to green algae, bare algae. Third, the oil cyan This is a relatively moderate fertilizer and water quality application of organic fertilizer, phytoplankton in diatoms, green algae and dinoflagellate a relatively balanced amount. Fourth, the brown tea This is also a kind of organic manure applied fertilizer water quality, high concentration of humus, phytoplankton to diatoms, cryptophytes, mainly algae, dinoflagellate, green algae are more. The above 4 kinds of water color are conducive to the growth of fish and belong to good water. There are also several bad waters that are blue-green-gray green and turbid, gray-yellow and turbid, off-white, dark brown, and reddish water. Many of these water-colored waters contain phytoplankton that are difficult for fish to digest, and there are too many suspended matter and dead organisms in water, which is not conducive to the growth and development of fish.