ashdavid;540784; said:
When I was still living in Australia ,I had kept at least 10 or more over the years and every single fish that I had that I tried to raise in fresh water eventually died. However, fish caught from the same area at the same time did very well in my full salt water set up and I got one of my fish to be quite big (around 30"). So can you back your statement up with scientific proof? These fish need salt water.
Hello Ashdavid, thanks for taking the time to respond to my comments. Here I'll list some information supporting my comment, and thanks for taking the time to read.
Back ground: I've kept my first L. argentimaculatus when I was 8, so about 20+ years ago, caught a dozen or so in Hong Kong during the mid 80's from the ocean to estuary creeks. Eaten them and seen them from 3" to 2 feet plus in supermarkets. I am currenlty raising one, for almost 30 months now, from 2" to 18" plus currently, eating everything in sight, kept in a variety of salinity and water conditions, but never anywhere near even "brackish" by definition.
References: I've always been very interested in fish that are amphidromous: I've actually written and corresponded with world renowned icthyologist Gerald Allen, and he stated that there are 3 species that he is aware that can live in pure freshwater indefinitly, including Lutjanus goldei ( which is found predominantly in freshwater, and sometimes in brackish), also its a very close kin to Lutjanus argentimaculatus, and lutjanus russelli, which can all live in freshwater.
In Hong Kong, these fish, 4 species of snapper fish have been bred and aquacultured for human consumption, raised in inland mud ponds, with minimal amounts of salt, for over 15 years already, and they sell them at 0.5kg-10kg specimens.
Lutjanidae snappers are secondary marine fish, having freshwater ancestral lineage. This is a eurahyline species and amphidromous or catadromous from literature.
Many of the semi-brackish fish move into open water of the ocean or deeper ocean for different reasons, including, but not limited to forage, escape predation, breed. For example, salmons, trouts, and chars, and many anadromous fish will go to the ocean to feed, grow large, return to creeks to breed, but they all have landlocked specimens that live in pure freshwater their entire lives and can breed the same.
More examples of amphidromous fish to boggle your mind: Oreochromis mossambicus the most common tilapia, can live and originates from pure freshwater environment, to hypersaline conditions of salton sea, 1.030 specific gravity. All salmonidae, many gobies, puffers. The guapote-large hericthys, found in Central America, if you look back at an old TFH article, they were found breeding in salt water pools near the ocean. The list goes on and on....I've also spoken to some field scientists down south america, stating that there are actually characins, pacus, piranhas, oscars, arapaimas, living in brackish water conditions, matter of fact, I have pictures of some, but I can post them, nor do they represent anything, but there is no reason why this guy should make this up.
These are just some supporting facts for my comments. Feel free to comment.
This was better written the first time, and my computer got unplugged accidently, and now I really didn't have the energy to rewrite it all again, but I might add a few comments here and there to support my theories. 
