There are a few:
Half-Banded Spiny Eel
Peacock Spiny Eel (According to CFC's care sheet)
Those are the ones I can think of off the top of my head.
Cheers,
GobyMaster
Try Tri-Mar. Go to the bottom of the tropical fish stock page, and theres normally a couple of species down there Ive had one of my eels from there, but the rest I got from BAS in Bolton. If there are any maidenhead aquatics near you (see their site) or if wildwoods, wharf etc is close to you then go for that.
even with a small eel the tetras would probably be eaten
I once bought a tyre track eel from trimar and it was great service
Well the eel I got from them was a zebra spiny eel, and none of the eels you mentioned (if they have been IDed correctly) will get anywhere near 18". They will stay under 8" IME.