Hello lex sorry not to reply to your message I have been on holiday.An HMA will not remove nitrate from water and would not come into contact with nitrite unless it was run by a power filter,the three stage is what I use and I can reccomend using one as they are superior in their capabilities against aquasafe type products that remove nothing but convert chlorines into other substances that can affect any meds you use.The devotedly discus is probably the cheapest around.