convert fresh water fish to saltwater?

[am3gross]

would it be possible to convert fresh water to saltwater? if it was done slowly of course....say over a 6 month span or even longer... just slowly raising the salanity over that span... i recently converted a mollie and i know they are brackish water fish, but after the mollie had babies the other day it made me wonder....

 

[E.intheC]

it really depends on the fish. Most freshwater fish will not do well long term with sea strength salinity. Some, like mollies, brackish puffers, etc will be fine, but most will not do well.

 

[IFbettas]

There are certain freshwater fish that can be kept in full marine but most of them wouldn't survive. Guppies and mollies are the most popular ones. There are several species of catfish that do well in saltwater too. Most of the brackish fish can be converted to full saltwater. Monos, scats, puffers, and gobies that are found in brackish water can easily adapt to a saltwater environment.

 

[anbosu]

I have had a guppy living in the sump of my FOWLR for 6 months now and I keep the salinity at 1.023.

 

[Luis A M]

It depends on the evolutionary history of each particular group of fish.Families that had recently (in geological times) colonized FW environments seem to keep some "osmoregulatory memory" and can be "returned" to SW if done gradually.Like cichlids,poecilids,ciprinodonts,atherinids.Others can not,as cyprinids,characinids,possibly anabantoids?.
With the inverse current trend to bring SW fish to low salinity,it would be no wonder that "mixed"SW and FW fish be kept together:worried2:
There was a company offering such "adapted"fish years ago...

 

[1DeR9_3Hy]

would it be possible to convert fresh water to saltwater? if it was done slowly of course....say over a 6 month span or even longer... just slowly raising the salanity over that span... i recently converted a mollie and i know they are brackish water fish, but after the mollie had babies the other day it made me wonder....

Free feeders

Ive read about people using mollys in ten gallons full SW as a source of live food for aggressive fish. It must work to some extent on the long term....

 

[anbosu]

Living in Florida you see a lot of species that can cross between freshwater and saltwater, especially in the rivers. It is fairly common in nature, but being able to replicate that situation in a tank is obviously different.

 

[temperatepuffer]

I have adapted mollies to SW tanks with no problems. In fact when introduced to the marine environment they started breeding even.

 

[NickTide]

Mollies and guppies definately can. I have seen sailfin mollies in the gulf of mexico on the coast of key Largo. I have also kept black mollies with my sea horses so that they supplied young as food for my horses.
Also, I used to work in a LFS that had this box of a "special" salt used to convert goldfish into full salt water. The box was on display and not for sale as it came from Japan and was made back in the 60's or 70's. I am guessing it was regular salt or sea salt with directions that told you to add the salt very slowly over months.

 

[Korrine]

There are some fish that can go from fresh to brackish, or brackish to salt or vice versa. The problem lies in the fact that they aren't supposed to live that way their whole life. Just because they travel there doesn't mean they can/should live there for life.

There's gentleman by the name of Neale Monks who has dealt a lot with brackish fish and this sort of thing. He has written books.