I have spent many hours nowe reading about Endlers ever since I found a Guppy / Endler hybrid in my
LFS.
They indeed do originate in Brackish water and in one of the 2 sites they are still found the water is not only brackish but contaminated by run off water from a rubbish tip on the shores of the lake they are in! Now I would not recommend trying to recreate those exact conditions.
The mere mention of Endlers will have Butterfly read this post however and I am sure she will respond with the links she gave me earlier on Endlers
I would post them for you but lost them when I had to replace my HDD in the laptop a few days ago.