Re: Ammonium

>From: gtong at sirius_com (G.Tong)
>Help. Where does ammonium come from? I thought ammonia was what the fish
>secrete. If so, something must first turn ammonia into ammonium ... Where
>does that something come from? TIA.

Aqueous ammonia (NH3) is always in equilibrium with ammonium ions (NH4+) in
water.  The exact proportion of ammonia to ammonium is determined by pH.  The
higher the pH, the higher the percentage of ammonia.  Ammonium is less toxic to
fish than ammonia, but for all intensive purposes, the ammonium content and
ammonia content are identical when plants are involved, since as the plants
remove ammonium, some ammonia is converted to ammonium to re-balance the

Please note that some plants don't do as well at the high pH levels that also
increase the ammonia proportion.  I have no idea whether the ammonia content
has something to do with this or if it's just a coincidence.

>A related question: when one has a biofilter in a heavily planted tank,
>would the bacteria and the plants be in competition? If so, who gets what
>first? My guess is the filter gets the ammonia first because it's puming
>the water through while the plants stand around waiting. Thus, the plants
>are more likely to get only nitrates--which we now know they have a harder
>time making use of.

IMO, yes.  The bacteria and the plants are in competition in a bio-filtered
tank in the same way they are in competition in a reef tank.  Since many
biofilters are very good at turning the tank water over, I'd suspect that the
bacteria would have the edge in most bio-filtered systems.

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc. Dallas, TX USA
(214) 575-3443 (voice)  MSGID:       DAWB
(214) 575-4853 (fax)    Internet:    dwebb at ti_com
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