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Nitrate uptake and can you believe the books

Susan Romano wrote:

>Ines Scheurmann states in her book "Aquarium Plants Manual" that: "Water
>plants do not absorb nitrogen in its elemental (uncombined) gaseous state,
>nor do they take it in as nitrate, as land plants do; rather, they take it
>in as ammonium.  Ammonium exists only in acidic water. In the normally
>slightly acidic environment of our aquariums, ammonium is unlikely to harm
>the fish, but in alkaline water it changes into poisonous ammoia. 

Just because you read it in a book doesn't necessarily make it so.
Particularly, unfortunately, when it comes to hobby literature.  Aquatic
plants can and do use nitrate, although as I said before, ammonium is the
prefered nitrogen source.

Several others have already commented on the ammonia/ammonium relationship.

>Horst and Kipper in "the Optimum Aquarium" said that: "Unfortunately we are
>still relatively helpless in the face of one aquaristic problem, and that
>is an over supply of nitrate... 

People in Europe have a different problem than we have in the U.S.  In most
places in Europe, nitrate in the water is quite high.  Combine that with
the fact that wether here or there, people tend to overstock their tanks,
it's easy to see why nitrate (and probably more importantly) phosphate can
be a reall problem.  

Even so, according to Clus Christensen, a well managed tank in Europe is
_still_ able to handle  the amount of nitrate and phosphate introduced with
water changes without creating algae problems.

>We know of a number of plants which accept
>nitrate as nitrogen and are able to use it, but on the other hand we also
>know of sone aquarium plants, such as many types of cryptocorynes, for
>which nitrate is useless. In general, nitrogen is needed by plants as
>ammonium.  If they receive nitrate, they must reduce it to ammonium."

I know of no studies proving that Crypts are unable to take up nitrate.
But even if it were true, it is rare that people have tanks stocked _only_
with Crypts, and most if not all other plants can and do use nitrate.  I'd
be interested to here from Neil and Paul on this subject, as they are the
only people I know who _do_ keep segregated populations of Crypts.