Currently Kraken and Rufus are being housed in a 15 gallon long aquarium filled with water from the well we have here on the property, which is mostly supplied by mountain runoff. It's honestly the best water you can use for aquariums in my experiences. It's naturally balanced, full of minerals, and best of all; no additives.
The tank will soon be too small for the two of them and I do have plans to upgrade to a 29 gallon at the minimum, but have my eyes set on a 55 gallon. Even that will eventually be too small for these two. Eventually they'll have to be separated as well.
Here's some facts about Kraken:
His egg was laid on May 20th 2010.
He hatched on August 3rd 2010.
He is a common snapping turtle (chelydra serpentina).
In captivity this species can live to nearly 50 years old.
They also grow very large, reaching up to 75 lbs.
Housing them can be difficult, and unless you have a very large and durable fish tank, it may be best to house your snapping turtle in a large plastic bin or even a large trash barrel.
They are quite temperamental and are highly aggressive. Here's a video that someone posted a while back. I can't take any credit for anything shown in the video and I will warn you: THIS IS EXTREMELY GRAPHIC AND DISTURBING!
Someday Kraken will be this ferocious. No one can save us!