In short, fresh water fish do not drink water; but salt water fish do. Why the difference? Most freshwater fish and saltwater fish maintain a salt concentration in their blood of approximately 10 parts per thousand (ppt), or 10 grams of dissolved salt per liter of water. Since freshwater fish swim in water with approximately 0.5 ppt, the chloride cells in their gills are designed to pump sodium, calcium and chloride into the fish. Therefore, they run a high risk of having their blood diluted if they drink water. Sharks. Since the fish’s skin is so thin, especially around places like the gills, external water constantly tries to invade the fish’s body by osmosis and diffusion. Because the fish is losing water, it must drink a lot to stay hydrated-but salty seawater is the only water around. Look at it this way: the two sides (inside and out) of a fish’s membrane skin have different concentrations of salt and water. I … Salt and water management in mammalian kidneys is a two-step process. It would die pretty quickly and traumatically. Some consider it to be a waste of money, not all that effective, or suitable for fish-only but unnatural for reef tanks, while others feel it does have its benefits for either type of system. First the blood passes through a microfilter system in a part of the kidney known as the glomerulus. To get rid of excess salt, the fish's kidneys pump lots of salt into its urine. Salt is a solute, which means that it is a substance that can be dissolved in a solvent; which in this case is water. Clown fish are those cute little orange and white fish you see at the pet store and can't resist watching even if you don't own an aquarium. Unless you just did a significant water change (today), your first step should be to do a 50% water change. Advertisement. Well, it all comes down to salt. By soaking fish for ten minutes in a sea-salt brine (1 tablespoon sea salt per 4 cups of cold water), he keeps fish on the grate from falling apart. They can also get rid of salt via their gills, and even their skin. When a fish drinks sea water, its kidneys (like ours) removes excess salt and gets rid of it via their urine. Fish have to compensate for the amount of water and salt in their bodies all the time through a process called osmoregulation. Using this method of treating water is quite controversial amongst aquarists. Freshwater fish (those fish living in fresh water, which doesn’t have a high salt content, like seawater) have blood with a higher concentration of salt than the water they are surrounded by. Putting a dying goldfish in salt water is not going to save its life under most circumstances. Make sure to add de-chlorinator and a little bit of aquarium salt (1 tablespoon for every five gallons.) Salt has been and is still used as a medicine for fresh water fish and it can do some very good things, but only some things can respond to salt. The question does come up whether these cute fish require a saltwater tank or if they can be placed into a freshwater tank and survive.