Eel identification please

I visited a friend of a friend who has a marine tank with three fish in it.
A puffer, one that looked like an angel fish (had a blue speck near his tail
where a spike came out) and an eel.
It was the eel I was fascinated with and would love to identify it. I can
only describe it as pretty much coloured like a zebra.
I filmed him in his small 'cave' believing him to be tiny and it was
brilliant when he lunged out to take some ham to reveal his minimum 3 foot
length!

Is it very difficult to maintain a marine aquarium?

Thanks for your help,

Dribbler
(the video I shot is 3 mins long and under 5megs if anyone wants to see this
eel attacking the ham and the angel, just email me after removing the
munging of my addy)