I think it would be neat to have a salt water tank but I am definitley not ready for the care involved in that. Check out www.fishlore.com. There seems to be a lot of info on that site. Will tell you what dwarf koi need; tank size, food, temp, etc. And actually a larger tank is better because they are more consistent. They won't see temp swings or chemical spike as easily, they are more forgiving.