Why dont fish dry up in salt water?

Question

Shouldnt fish dry up since they are surrounded by salt water? (Water wants to diffuse towards higher solute concentration. IE: salt) Is their body not permeable to water at all? Seems like the same thing should happen to them that happens to a slug.

What about when they drink the salt water? Wouldnt their cells dry up because the water in them would diffuse out of the cell (towards the higher salt concentration outside of the cell) Again, this is what happens to us when we drink salt water. Why doesnt it happen to fish? (Unless maybe they dont drink but get their water from eating?)

Thanks.

Im guessing they have higher salt concentrations in them (about equal to ocean water). This would explain why they die when placed in fresh water. The water outside their body wants to come in (higher salt concentration inside the fish) and they fill up with water and die.

Answer 1

You answered your own question already. As a matter of fact I believe that salt water fish will actually burst when put in fresh water, just like a ballon. I believe some fishes will do this, not all, but I'm not sure since I've never been cruel enough to try.

Answer 2

Actually, yes you can change it over to a salt water tank. You will need to get a hydrometer. your filter is fine for your size tank you do not need a protein skimmer. I have a number of salt tanks and my 30 doesn't have a skimmer and never did. You may want to pull your carbon out of your filter and replace it with a filter media without carbon. to convert your tank, you will need salt. you will have to mix the salt into a bucket at a higher rate. On your hydrometer you want your new dissolved salt water at 1.4 that will be 10 galllons. Remove the 10 gallons from your fresh water tank and add the new premixed salt water to your tank and let the filter run. After an hour test your salt water with the hydrometer. It should be around 1.001 or so. That is fine since now your tank has to run empty anyway. you will also want to get a salt water test kit. Your tank will still have to cycle. In one week you will want to do another water change. Be sure to mix the salt for the salinity required by the shrimp you are going to get. Your ammonia is .5 or less nitrates 20-40 or less and the PH around 8 (if your PH is too low add a few sea shells to the water this will bring the PH up) You can also think about getting live rock. Good luck with your salt tank.

Answer 3

Fishes are able to live in saltwater without "drying up" because they are capable of osmoregulation.Osmoregulation is the active regulation of the osmotic pressure of bodily fluids to maintain the homeostasis of the body's water content; that is it keeps the body's fluids from becoming too dilute or too concentrated. Osmotic pressure is a measure of the tendency of water to move into one solution from another by osmosis. The higher the osmotic pressure of a solution the more water wants to go into the solution. The pressure that must be exerted on the hypertonic side of a selectively permeable membrane to prevent diffusion of water by osmosis from the side containing pure water.

Animals in all environments (aquatic and terrestrial) must maintain the right concentration of solutes and amount of water in their body fluids; this involves excretion: getting rid of metabolic wastes and other substances such as hormones which would be toxic if allowed to accumulate in the blood via organs such as the skin and the kidneys; keeping the water and dissolved solutes in balance is referred to as osmoregulation.

Two major types of osmoregulation are osmoconformers and osmoregulators. Osmoconformers match their body osmolarity to their environment . It can either be active or passive. Most marine invertebrates are osmoconformers, although their ionic composition may be different to that of seawater.

Osmoregulators tightly regulate their body osmolarity which always stays constant and are more common in the animal kingdom. Osmoregulators actively control salt concentrations despite the salt concentrations in the environment. An example is freshwater fish. The gills actively uptake salt from the environment. Water will diffuse into the fish so it excretes a very hypotonic urine to expel all the excess water. A marine fish has an internal osmotic concentration lower than that of the surrounding seawater so it tends to lose water and gain salt. It actively excretes salt out from the gills

Answer 4

They osmoregulate!