Mkay, if you aren't nuts about our friend here,
The Blue Whale
you obviously don't know enough about him.
They are the fastest creature in the sea, swimming up to forty knots. It is the largest animal on the planet. How big, you ask? Its heart is roughly the size and weight of a Volkswagon. Some of its veins are so large around that a child would be able to swim in them. Its tail is the span of a small plane.
I think the most amazing thing about the blue whale, is that, despite its size and power, the blue whale eats tiny little organisms and is extremely peaceful.
AWESOME.
They aren't from the sea. They are freshwater fish, if my memory serves me.
But we've already had a few in here that are freshwater. For example, the black ghost knife I had for seven years in a freshwater tank, so I don't think that it's saltwater.