NH3 vs. NH4, what's the difference?

[marcelft]

Whats the difference between NH3 and NH4? My water has no NH3 but does have about .2 NH4...I think...Im confused...I posted before about my city water having chlormine in it. I got a filter from filter guys, but I still have ammonia showing in my RO water when I test it for "Total ammonia test" with reagent.

 

[Randy Holmes-Farley]

They are just two forms of the same chemical (ammonia) in which the ratio of the two depends only on pH. I'd always focus on the total (NH3 + NH4+) because a kit will detect the higher total levels easier. You can easily calculate the free ammonia (NH3) if you want to know it since it is true that the free form is more toxic.

I discuss these issues a lot more here:

Ammonia and the Reef Aquarium
http://reefkeeping.com/issues/2007-02/rhf/index.php

Is this an RO only, or RO/DI? If a new DI, did you run a gallon or so of water through it? Or might the DI be depleted?

All of these can result in ammonia readings if there is chloramine in your tap water. This has more:

Chloramine and the Reef Aquarium
http://www.reefkeeping.com/issues/2003-11/rhf/feature/index.php