I found 2 links that may be of use to you.
I seem to have found very little online about the ghost knives, so I can tell you what I know from research and study, and taking care of them.
They get large, up to 19 inches, and need a large tank. Minimum tank size should be 125 - 150 gallons by the time they're fill grown. They're usually shy fish, and they give of an electric current that helps them to find prey. I have an article here somewhere, I'll have to look for it. It explains about the electric current in the knife fishes. Basically, it's used as a hunting technique. They are able to shock smaller fishes to stun them so they can eat them, and it also helps them to sense for the food, too. I'm not sure what you've got available to you for live foods, but feeder guppys and live BLACK WORMS (not to be mistaken for bloodworms, they're different) and tubifex worms, seem to be their favorites. They need a lot of hiding places, lots of territory to call their own. You'll want to keep it with peaceful tankmates, because they are nearly blind, and long term, they don't like to be with others of their kind. They fight until 1 wins.
They like warmer temps, 79 - 82F, and need softer water (lower pH) than the standard community fish, no higher than 7.0. Long term without proper water parameters, they get sick. And, they're very sensitive to water quality. Ammonia and nitrite levels will cause sores and kill them fast, and high nitrate (over 60) longterm will also kill them.
They have a long life span, and can live into their 30's & 40's easily if properly cared for.