If it IS that eel (and it might not be there are lots similar), 15" wild size (fishbase), so around 10 captive size id guess is right.
Id expect them to tolerate harder water, but otherwise much the same as any other spiny eel - live or frozen bloodworm/brineshrimp etc as food, dont waste your time trying to tempt with pellets or flake, it wont happen.
Provide a tank with a soft substrate, no sharp gravels, not too bright (all my eels enjoy a covering of floating plants and thus stay out of the sand, without the cover they spend all their time hidden and are not happy this way.)
Wont compete well with fish who eat faster, generally speaking (although BIG eels compete just fiiiiiiiiine, they also tend to eat their competitors if they can).