Hypothetical question, curiosity only.

[evilxyardxgnome]

My mollies lasted a few months before my tomato clowned killed em.

 

[benzjamin13]

I think it has to do with their gills and how they intake oxygen.

 

[lilfats2]

learn something new everyday mollies are brackish... hmmm

 

[sg1]

My mollies lasted a few months before my tomato clowned killed em.

I gave up on molly's more than 10 years ago, I found that pretty much anything I put in the tank with them ended up killing them lol

I think it has to do with their gills and how they intake oxygen.

Thats pretty interesting. Wish I had a time machine, go back and become a marine biologist, I find all this stuff facinating.

 

[Bobears]

I can tell you that there are some types of therapies for disease by where a freshwater fish is dipped into normal salinity sea water to cure it of parasites and the like. But, from what I understand you had better know what your doing or else. I think they are dipped till they start to show real stress, 2min or so. Just something I heard.

 

[Modest_Man]

Wonder what it is exactly about their biology that makes saltwater fish so intolerant to freshwater and vice versa. To above poster, did they live for a long time?

It's all about osmosis.

Skin is a semipermeable membrane, meaning that water can flow across it but larger molecules (like salt) cannot. Osmosis is the process by which water diffuses across a cell wall or membrane from a low concentration to a high concentration.

In freshwater, there is a higher concentration of molecules inside the fish vs. the water, so the fish is constantly expelling water from its system as water is constantly moving into its body, trying to equal the gradient and keep its cells from becoming turgid (swollen and bursting with water).

In saltwater the opposite is true, there is a higher concentration of molecules (salt) ouside the body so the fish is forced to constantly consume water to keep it's cells from becoming plasmolyzed (shrivled and dry).

In this diagram the cell on the right would be a freshwater fish in saltwater, and the cell in the middle would be a saltwater fish in fresh. The cell on the left is a normal cell.

Some fish are anadromous and can survive in both as their bodies can regulate both ways. Salmon are a prime example of this. Several cichlids can do this as well, including tialpia, uros, and some Nandopsis.

I can tell you that there are some types of therapies for disease by where a freshwater fish is dipped into normal salinity sea water to cure it of parasites and the like. But, from what I understand you had better know what your doing or else. I think they are dipped till they start to show real stress, 2min or so. Just something I heard.

That's because the fish's cells are stronger than the parasites, and the cells of the parasite will lyse (burst) effectively killing it. Too long in the salt bath and the fish's cells will lyse as well, killing it.

The process of which I just posted above.

 

[cookiemonster]

Haha, I was just going to post that, but you beat me to it. Great info as usual Modest Man.

 

[Modest_Man]

What can I say. I'm an effing biologist.

 

[Cich_lids]

black belts are found in full salt as well. I saw a convict that lived in a salt tank for months he was supposed to be a feeder but was to fast and smart.