It depends: Maybe you haven't changed the water in a while and your fish isn't use to th new clean environment, maybe you changed too much water, or the fish is uncomfortable.
If a fish is acting lethargic than you should do a large 50-75% water change pronto. Also, try using an aerator in the tank to try to raise the dissolved oxygen levels.
The fish will look and act lethargic, also you can tell if the water is bad by doing some simple water quality tests.
Change its water. When a fish gets lethargic it is a sign that the water is bad. Please keep in mind these basic rules :- 1 inch of fish needs at least 1 gallon of water . All fish need a cycled filter running 24/7. Every tank needs to have at least 50% of its water changed weekly. If you are not doing ALL of the above things your fish will die. Every successfull aquarist knows and lives by the above rules.
Fish that are active, with fins up, and swimming around. Fish that appear lethargic, have their fins clamped, or they are gasping for air is a sign of ill health that may be caused by bad water quality
Yes it is quite normal.
It is recommended to change the water in a fish bowl at least once a week to maintain a healthy environment for your fish.
put the live fish in a bag filled with water and change the tank then put the fish back in.
You should change the water in your fish tank every 1-2 weeks to maintain a healthy environment for your fish.
Yes they will die because tropical fish are kept in an aquarium with heat control for the temperature of the water, they will not survive in cold water. Put a tropical fish in cold water it's metabolism will slow down to the point its body no longer works, it won't be able to digest food, will become very lethargic, and die.
Harbor seals are not typically lethargic in water; they are quite agile and can swim efficiently. They often engage in playful behaviors, such as swimming and diving. However, they do spend a significant amount of time resting or basking on land or ice, which might give the impression of lethargy. In the water, they are alert and capable hunters, primarily preying on fish and invertebrates.
well if its cold water fish then 3-4 days :)..
You should change the water in a fish tank regularly, typically every 1-2 weeks, to maintain a clean and healthy environment for the fish.