Partial water change: first, prepare the spare water for water change 4 ~ 6 days ago. After the standby water is available, remove the easily damaged equipment such as thermometer, heating rod and automatic temperature controller in the fish box, and wipe the moss on the four walls of the fish box with gauze. Stop for a few minutes and let the residue in the water settle down. Then, use a quarter hose to pump the water out of the fish tank, generally taking half of the old water as the standard. In the process of pumping water, try to put the suction end of the hose close to the dirt at the bottom of the box and pump out the precipitated dirt. Use a water thermometer to measure whether the temperature of the standby water is consistent with the water temperature in the fish tank. If it is consistent, it can be injected into the fish box; If the temperature of the standby water is low, some hot water can be added to make the temperature of the standby water consistent with that of the old water in the fish tank, and then water is injected into the tank to restore the original water level. Pay attention to make the water level of standby water higher than that of fish tank. With a siphon, insert one end of the pipe into the standby water, and put the other end into the water in the fish tank, so that the water outlet hole of the pipe is upward, so that the injected water has the minimum impulse, and the standby water slowly flows into the fish tank to avoid washing away the dirt and aquatic plants in the sand. Otherwise, although some water has been changed, the water in the fish tank is still turbid. The time of local water change depends on the water quality and water transparency in the fish tank, and it is generally appropriate to change it once every one or two months.

Change all the water: the water in the tropical fish tank is used for too long, sometimes it takes more than 5 ~ 6 months to change all the water. A large amount of fish droppings and decaying substances are deposited in the sand at the bottom of the water tank, and even some biogas is produced. These things not only affect the transparency of water, hinder the line of sight, but also cause changes in water quality and pH value. Because of this, fish's activity ability drops, their appetite loses, and they can't even survive. At this time, all the old water in the fish tank must be replaced. First, put tap water into an empty water tank and let it stand for a week as standby water. The standby water is ready, and the water is changed. Step 1, turn off the electrical switch and take out all aquatic plants and thermal insulation equipment in the fish box; Step 2: Remove all the fish from the water tank and put them into standby water to prevent the fish from jumping out and falling. The third step is to pump all the old water out of the fish tank. Step 4: Wash the sand or stone in the fish tank repeatedly with the water you bring, and then drain the dirty water in the box, smooth the sand or stone with your hands, spread a white newspaper on the sand or stone and cover it tightly. First, add some spare water to the fish tank with a bucket, then drown the white newspaper, which is about 1 ~ 2 cm higher, and then add water with a siphon. After the fish tank is filled with water, gently take out the white newspaper, plant aquatic plants on sand or stones, and put them into heating rods or other insulation equipment. When the water temperature in the fish tank rises to a temperature suitable for this tropical fish (it must be measured with a thermometer), all the fish will be put back into the original fish tank, and the net cover will be put on the tank cover, and all the water changing work will be completed.