Quote Originally Posted by critter crazy
From my understanding with my own fish(no bettas tho) that you are not supposed to put any store bought water into your tank! I have never put any store bought water into my tank, and all of my fish are very healty. Store bought water can have bacteria and disease in it!
That's true; its called cross-contamination. Though if a fish is diseased to begin with, it will transfer to the tank regardless.