E cats are fantastic fish and can have a lot of personality, mine is hand tame and will accept food straight from your fingers above the water line, he also begs for food and attention by splashing with his tail and rubbing his snout against the glass.
The downside is they are electric, this means they can have no tankmates and you have to be a bit more sensible about tank maintainance, especially when they get to over a foot long and start to pack a bit more of a punch. When i first got my e cat he was a tiny 5" fish and the shock was only a little stronger than the one you get if you stick your tounge on the terminals of a 9v battery, now he is 18" a shock sits you on your backside and leaves you with a numb arm for a couple of hours, it isnt pleasent. Try to keep hands out of the water as much as possible and when its unavoidable keep wet time to a minimum.
They arent the most active of fish so huge aquariums arent needed, though obviously you have to match tank size to the size of the fish. A tank of 48x18x18" should do one for life though you should be prepared for the unexpected and have the means to upgrade if needed as in the wild they can reach 4 feet.
