First of all, greetings from South Africa!
I have had a freshwater moray eel before, when you see this in a LFS you def going to buy it right. Anyhow, i did research on it and found out that this eel does not exist. There is no such thing as a freshwater moray eel. The Moray eels live in the sea, but when they breed or give birth they come into estuaries (brackish water) and even freshwater, as there are less predators for there young and more food. This is where the people catch the young morays and tell the supplier/LFS they caught them in freshwater, hence the name. After maturing in the estuarie, they do return to the marine water. The Moray eel i bought lived for about 2 months, then died, as it went on a food strike, this is common for the freshwater morays when they not in the right conditions, he also moved around the tank quick abit swimming in the open, which is not normal for a moray eel, or any eel really(with exceptions, ie. tiretrack,etc). So in the end they die of starvation due to living in freshwater.
However, evolution does exist and im sure by now there are a few morays that have been bred in freshwater and are now fully adapted to freshwater. I now bought another about 6months ago, from a guy who said the eel is in complete freshwater and is eating and growing, so i checked it out and eventually bought the eel. I have had him now for about 6 months and he is growing and eating like theres no end! And he hides most of the time but is getting a lil friendlier with me. I do not see him dying on me anytime soon (touch wood)! The only problem is that he only eats live food (comets) and im trying to get him off it, but i feel as if im fighting a losing battle. LOL
I love him to bits! He is about 1meter in length and quite thick as well!
Hope i cleared up a lil confusion.