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
put the live fish in a bag filled with water and change the tank then put the fish back in.
Yes it is quite normal.
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.
well if its cold water fish then 3-4 days :)..
When you are changing the water in a fish bowl, you have to empty cup ot bowl with water in it. Then, put it into clean water.
It depends on if you are doing a complete water change or a partial water change. I usually just leave the fish in and siphon off about half of the water than replace the water. The fish get a bit nervous but seem to be fine with being left in the tank. To answer your question: No, you do not have to remove the fish when changing the water.
If there is no overflow of water, then the container's over-all weight goes up by the weight of the fish. The weight of the water itself doesn't change.
Every month.