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).