I use Instant Ocean. I have no issues with PH fluctuation, which I have heard can happen with some salt. It is relatively inexpensive, which the way I do water changes so often, is a huge plus. Some folks have said they spend almost a hundred dollars per 50 gal bag/bucket. I can't see it, but as I stated elsewhere today, alot of people feel the need to spend the most to get what they feel is quality.