So, I just bought a Betta to join my Mollies. She is very small, smaller than my mollies. She love swimming back and forth across the bubbles. Mollies prefer brackish water, but I haven't added salt yet because I wasn't sure how it would affect other fish that I plan to buy in the future. The Petsmart instruction flyer said it wouldn't harm other fish, but I want to make sure. Will brackish water kill a Betta and/or a snail?