when a fish take in oxygen which is dissolved in water ,how does it maintain its water balance in the body?

Question

when a fish takes in oxygen at the same time water also enters its body so how does it maintain its water content

Answer 1

The air and water are passed out through the fish's gills. The gills have a lot of projections from them (gill filaments) that have a lot of blood vessels very close to the surface. Some of the dissolved oxygen is absorbed through the skin of the gill filaments and passes through the blood vessels into the blood where it can be carried to the rest of the body, or "stored" in the swim bladder, which is used by some fish to help with their ability to stay at a certain level in the water. In some fish, the bladder is "closed" so the only way to get air into it is by the method I've already described. Other fish have an "open" bladder and can "gulp" air at the surface of the water as well.

So when a fish takes in oxygen, it really isn't taking in water - that all goes out through the gills.

Some fish also use part of their digestive system or can get a limited amount of oxygen through their skin.

Answer 2

Fish pee a lot. That's where high amonia content comes into place. Fish waste turns into amonia, which is why the water in the tanks have to keep at certain levels of PH. Too high of a PH means the water is too acidic (amonia, etc.) Check your PH regularly, and maintain water changes, otherwise it's toxic to the fish, like if we were to have to drink and bathe in our own poop and pee.