if you mean "Moringua arundinacea", the Bengal spaghetti eel, it is generally considered a Brackish fish as it resides in esturies. You could probably keep it in a fully marine tank as long as the salt level wasnt too hight although obviously it is not the ideal ecosystem for it.
They get over 2ft in length and tend to be very slender hence the name.
As for eating your other fish and shrimps, well this is always a possibility, but as eels tend to be virtually blind you'd probably find that the chromis and clown would evade it, at least for a while, however if they were caught un-awares at night they would be a gonner. Same goes for the shrimps.
Ben