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Re: Water chemistry in tanks vs rivers

Frank I. Reiter wrote:

>From: "Frank I. Reiter" <FIR at istar_ca>
>Subject: Water chemistry in tanks vs rivers
>> Date: Sat, 7 Mar 1998 06:59:04 +1000
>> From: David Aiken <d.aiken at eis_net.au>
>> Plants and algae grow when there are enough of *all* the necessary
>> nutrients available. If one nutrient is not available in sufficient
>> quantity, growth slows or stops.
>Yup, I've got that.  I guess I just have trouble thinking that there was 
>excess phosphate available in this river.  I have heard before concern 
>about high nitrate levels in natural bodies of water.  Is it common for 
>phosphate (or some other source of phosphorus) to be plentiful in these 
>water bodies?
>> Now, the big difference between streams and aquariums. A plant in a
>> stream is bathed in a constantly changing flow of water. 
<big snip>
>As you say, others have maed this point before, and at first I accepted it 
>as sounding logical.  After some thought though it just doesn't make sense 
>to me.
>I can see how *maintaining* small concentrations in an aquarium would be 
>very difficult due to the consumption of that plants in a small amount of 
>time being a higher proportion of the total amount of that nutrient in the 
>water, but if one *does* maintain a given concentration then I really don't 
>see what difference the total water volume makes.
>If a plant in my tank, and another in the river both have 10ppm of nitrate 
>in the water that they are touching, and if both are in sufficient current 
>that new, 10 ppm water is alays flowing over them, then why should it 
>matter if there is another billion gallons upstream or not?

As you indicate, it can be difficult to maintain the 10ppm consistently 
in the aquarium - plants and algae are continually depleting it and you 
may, in a heavily planted aquarium with a low fish load, be forced to 
supplement the nitrogen available to your plants by nitrate additions. In 
a river with those billion gallons upstream, supplementation will never 
be an issue and the nitrate level in the stream will remain much more 
constant than in the aquarium.

If the aquarium has enough nitrogen sources/inputs and a low plant load 
so that there is a shortage of outputs (plant trimmings, etc), you will 
have the exactly the same situation as present in the river in terms of 
an "inexhaustible" nitrogen supply. If the other necessary nutrients 
including phosphorus are also present in sufficient quantities, as they 
obviously were in that river, you will get the same result - lots of 
algae over everything. Many aquariums, especially fish only tanks, are 
actually just like this.

Of course, that's not the situation we're trying to encourage <g>.

David Aiken