Why the sea water fish can't survive in fresh water?

We have 3 goldfish and 2 loach and after 2 days the water turns cloudy.
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Bacteria in your tank isn't a bad thing. In fact, it is needed to break down waste and maintain healthy water conditions. The balance between microorganisms and the fish in your tank is what keeps harmful chemicals under control.
of How to Change the Water in a Fish Bowl was reviewed by  on March 15, 2017.
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Since times humans have exploited certain anadromous fishes during their migrations into freshwater streams, when they are more vulnerable to capture. Societies dating to the are known which exploited the anadromous fishery of and other . In the tribe has harvested migrating along the since prehistoric times. This fishing practice continues to current times, and the has supported research to assure the water quality in the Truckee can support suitable populations of the Lahontan cutthroat trout. Fish gasping for air at the water surface could be a sign of nitrite poisoning.
Photo provided by Flickr1 teaspoon of salt per 300 Gallons of water can help the fish to cope with nitrite toxins.
Photo provided by FlickrFreshwater fish compatibility chart and characteristics of different types of fish.
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There really is a reason that I harp on about not letting the petstore's water into your tank. The pet store has a lot of fish comingin and going out, and can easily get a in the water that is just waiting fora stressed out fish to attack. By keeping as little of the store'swater from mixing with yours, you minimize the chances of your fishcatching one of these diseases. The fewer diseases you get in yourtank, the less money you spend on . Some fish species can live in both freshwater and saltwater. These species are called euryhaline fish. However, most fish species can only survive in one or the other based on their salinity tolerance, or how much salt their bodies can handle.Around 400 million years ago, fish left the water and started to evolve into land-loving creatures. But how did the transition happen? A new and unusual experiment could shed some light on the kinds of changes that enabled fins to become limbs. Researchers took a fish species known to be able to walk on its fins from time to time, and raised it on land. Watch the fish promenade in this Nature Video.

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Read the News & Views: Catadromous fish, on the other hand, generally live in freshwater and only enter saltwater to spawn. North American eels and European eels fall under this category, according to the National Marine Fisheries Service (NMFS). There are two main types of euryhaline fish: anadromous and catadromous. Anadromous fish are but spend most of their lives in the sea, only returning to freshwater in order to spawn. These fish include salmon, smelt, shad, striped bass, and sturgeon, according to the Alaska Department of Fish and Game. In fact, freshwater fish will often be unable to survive if the reaches more than .05 percent, according to the National Biological Information Infrastructure (NBII).