To tell you the truth, y mate keeps discus in it and recons that its as good as RO. Im not sure and so thought i would ask on here.
It probably means more to the discus fans.
The RO filter will remove 99.9% of everything in the water, making the Ph around 6.2 depending on where you live. The HMA filter will remove the heavy metals and the Chlorine, which are extremely harmful to discus. The HMA will not alter the Ph which is ideal, because we can use that to blend with the RO water to make the correct Ph.
It looks to me like it would be a good addition to an existing RO system.
but I havent seen anything that says it is a good stand alone replacement for RO.