De-ionized water for phrags?

[mspatt]

I am trying to spread the joy of orchids to my husband. He has a few phrags of his own. Someone told us water from his many aquariums was great for the chids. The plant died and someone else said it was "salts". HmmmmToday he came home with an empty Coke bottle that was filled with "de-ionized water". I'm not too sure about this, but said I would ask on the forum-- Anyone know what that is and if it would be good for the phrags??