Re: Ammonium

Subject: Ammonium

> >Plants generally will not use nitrates due to the amount of ene
> >required to extract nitrogen from the compound.  They much pref
> >ammonium as the nitrogen is less tightly bound.  By removing th
> >biowheel, there are less nitrifying bacteria to convert ammoniu
> >the conversion goes slower, giving the plants a better shot at 
> >it.
> Help. Where does ammonium come from? I thought ammonia was what 
> secrete. If so, something must first turn ammonia into ammonium 
> does that something come from? TIA.

Within the normal pH range of a planted aquarium, ammonia and 
ammonium are both present.  The lower the pH, the more ammonUM, 
the higher the pH, the more ammoniA.  That's one of the reasons 
that it makes sense to keep the pH in the tank a little below 
neutral.  At that pH, it is mostly ammoniUM, making it easier for 
the plants to utilize.  As an added bonus, ammoinUM is not very 
toxic to fish, while as we know, even small amounts of ammoniA can 
be deadly.
> A related question: when one has a biofilter in a heavily plante
> would the bacteria and the plants be in competition? If so, who 
> first? My guess is the filter gets the ammonia first because it'
> the water through while the plants stand around waiting. Thus, t
> are more likely to get only nitrates--which we now know they hav
> time making use of.

Which is why it makes sense to use as little biological filtration 
as is practical ;-)  As George mentioned, there are times where 
people prefer to heavily stock a planted tank. (as is very often 
the case when Discus are kept in a planted tank... Their size and 
waste output puts a big strain on the plants to keep up)  In this 
case, the plants probably get enough ammonium anyway, but there is 
more than they need.  So you process the rest through a biofilter, 
and remove the less toxic (some maintain non-toxic) end product, 
nitrate, by doing large, regular water changes.

Karen Randall
Aquatic Gardeners Assoc.
Boston, MA