Why does a sea fish die when put in tap water?

Answer 1

Well, first thing is tap water is freshwater and Saltwater Fish die in freshwater and vice versa. Secondly there are amounts of chlorine in tap water to make it safe for us which is deadly to fish.

Answer 2

Tap water is not very good for fish. There are two main reasons.

Most tap water has been treated to ensure it is safe for us to drink. This treatment usually leaves some chlorine (in some form or other) in the water. Chlorine is a poison for us and for fish but the level of danger for fish is very very much lower as they are passing water through their gills constantly and because they are so (relatively) small.

Secondly, tapwater has little oxygen dissolved in it. This depends on how far your tap is by pipe from the open reservoir. We get our oxygen from the air; fish have to rely on the oxygen dissolved in the water that they pass through their gills. Both these problems mean that a race starts when you place your fish in tapwater. Will the water improve fast enough for the fish to live or will the fish die first? Sometimes the fish wins but it will suffer.

Before placing tapwater in an aquarium it should stand open to the air for 24 hrs. This will allow the chlorine to evaporate and the oxygen from the air to dissolve in the water. There are some additives that will ensure that tapwater is safe for fish, available at your local pet shop.

Answer 3

Tap water may contain chlorine, a poison to kill germs. Even if it is not chlorinated, many sea fish are unable to live in fresh water.