They need a very big tank. It won't take 100 years to get to be too big for most tanks.
This is mine in a 72g. I think it's fair to concede it's outgrown the tank. I'm currently saving up for a (much) larger setup for it.
The 30" one that I saw in a tank, the tank was in a public aquarium and approximately 25 feet long by about 8 feet deep (front-to-back) and maybe about 5 feet tall. Man, now THERE's a tank I wish I could have in my basement.
