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Re: Of fish loads and nitrogen
You can add nitrogen to your tank. The purpose of this is to reduce the
phosphate to a level which will no longer support algal growth ... the
reason that we target phosphate as the limiting nutrient is that it is
commonly limiting in natural environments so that plants have developed
strategies for 'hoarding' it. Of course you can try limiting other
nutrients such as nitrogen but this is difficult since even with no
nitrates in the water, blue greens can still fix N2.
When Paul and Kevin first wrote their article on PMDD and their algal
experiences, they asked me to explain how higher plants could outcompete
alga for phosphate. I couldnt answer but have thought about it and done
some reading since then ... in my opinion the key element is not that the
plants can compete successfully for available phosphate with the alga
(they cant since uptake rates are much higher at far lower concentrations
in algae than in higher plants) but that they can sequester it for far
longer time periods. In effect, the turnover rate in alga is much faster
than in higher plants. This means that over time, even though at any
given instant the alga take up a greater proportion of available P, all
the P in the tank is slowly absorbed by the higher plants. This is
obviously a slow process which is why patience is required in the
Sears/Conlin approach. This will be even slower if you have a significant
amount of P in your tap water ... I would suggest a phosphat absorbing
filter in your tank along with floating plants to strip the water of P
even faster (along with the addition of nitrate).
dave.