I have a 12" snowflake eel in my 75-gallon FOWLR right now. I would recommend as large a tank as you can get, since a snowflake eel may outgrow a 53-gallon tank. From what I have seen, I do not think the shape of the tank matters too much for an eel. Make sure to include a screen cover or lid, since eels are known for being masters at escaping.
Care seems to be fairly simple through basic water and tank maintenance as well as feeding every other day or so. I used to feed chopped-up raw shrimp to my eel, but I recently switched to homemade frozen blended seafood for the tank, and some of the pieces are large enough that the eel eats them as well. The disappointment with this is that he no longer comes all the way out at feeding time. He used to get hungry about every other day or so and would swim up near the top and slither through my small mangroves awaiting shrimp bits. Now he just stays in the rocks and sticks his head out to grab bits as they come by, so I do not see more than his head very often.
