Re: Nitrate Mass Balance

[Roger Miller <roger at spinn_net>]

On Friday 18 October 2002 04:24, Dave wrote:

> In other words for plants to clean a tank with 30ppm NO3 to 0 ppm NO3 the
> plants would need to grow 1800 grams or about 4 POUNDS WET.  If I'm wrong
> on these calculations it would be the estimates for % H2O in an aquatic
> plant and the % N in an aquatic plant but I shouldn't be off by much.

Dave,

I don't think you're far off, but here are a few things to consider.

As you expected, the calculation is very sensitive to the amount of water you 
assume the plants contain.  I think if you assume that the plants are 97% 
water instead of 98.5% water (either of which is in the range of reality) 
that your estimate will be cut in half.

Denitrification is probably at work to one degree or another in most planted 
tanks.  Just how much effect there is from denitrification would vary quite a 
bit from tank to tank, but there will probably always be some.

Aquatic plants can grow quickly when supplied with enough light and carbon.  
In most cases a 100 gallon tank won't produce 4 pounds of wet plant matter in 
a week .  It might take a month.   I don't think it would be unusual for a 
100 gallon tank to produce almost a pound/week of wet trimmings, and I think 
that would put the nitrogen consumption in the range that many of us observe 
in our tanks.

Roger Miller