Don't quote me on this... but I would have thought that it was just a lower concentration in the bottle to make it easier to measure out for bowls. Kind of like Bettafix (o.2%) and melafix (1.0%). The same thing, with the same active ingredient, but different concentrations. Measuring water conditioner from the same bottle for a 10 gallon tank and a 1.5 gallon bowl is pretty difficult. Either you have to add a TON of conditioner to the 10 gallon tank... or a couple drops to a 1.5 gallon bowl....