Update on your synbranchus marmoratus ? I have one that is slightly smaller than these. Info on them is hard to find. Hoping you reply to this after it being posted so long ago!I don't think it's an Anguilla, it has no pectoral fins. I purchased 3 eel less than a month ago that were labeled as a Marbled Anguilla(spelled horribly wrong on the tank). But I'm pretty sure what I bought was a Marbled Swamp Eel, Synbranchus marmoratus.
Although now that I look at more pictures, I might have received two of the three different species of Synbranchus.
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252005000300001
Yours might be Synbranchus lampreia, but I don't see any photos online that show the stripe down the back like yours.
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