Another option is to move fish out of the old fish tank and put them in the new fish tank, reducing the fish's distress. and prevent fish from harming workers (In the case of a large fish or have spines/hard fins ray that are sharp) Anesthesia may be used to keep the fish calm. Or make the fish unconscious before moving the fish. (Depending on the size of the fish and the chance that the operator may be harmed by the fish) you should refrain from feeding 1-2 days in advance. After that, the water level in the fish tank should be reduced to a level that just covers the backs of the fish. About 6-12 inches (depending on the size of the fish) then use fish anesthetic mixed with some water from the fish tank and then in an outside container before putting it into the fish tank. By allowing the anesthesia to spread and mix with water throughout the fish tank. along with turning on the oxygen machine at all times Observe the fish's symptoms to see if they reduce their response to stimuli (they are calm) or they become unconscious (they stop moving. not responding to stimulation) and then take the fish out to a new glass tank. Use clean water with a temperature not different from the water in the tank to wash the fish and gills to remove the anesthetic stains. away from the fish Until the fish begin to recover and begin swimming, then release the fish into a new fish tank. The type of anesthetic I've used that works well and is highly effective for many freshwater fish in the tropics is clove oil. It is mixed with 95% ethyl alcohol in a ratio of 1:9 by volume to make a stock solution for use as a fish anesthetic. In using fish anesthesia, the laws of each country/state should be taken into account as well.
Nawin.