Marosatherina ladigesi is a very easy to keep fish, as it prefers the more hard alkali conditions that constitutes most tapwater, they do not, however, tolerate pollution well so good water quality is important. Eat pretty much anything, peaceful, active, and as stated above, as they age, the dorsal, pectoral and anal fins extend and can get very long filaments.
I used to keep these when I lived in England. I lived on the Surrey/Hampshire borders where the water was so hard, you cut cut wood with it! Straight out of chalk boreholes. As I don't like cichlids, rainbows became my thing there. These were one of the first I got. Never tired of them, nice fish.
PFK had an article about them a while back, I'll see if I can find it.