Re: Phosphates/ Chemistry

2 ppm  is a HUGE amount of phosphate! Freshwater is considered 
hypereutrophic at 0.1 ppm. The only place you find phosphate at that high 
a concentration in natural systems is in sewage effluent. Your target 
phosphate concentration should be in the range of 0 to 30 ppb (micrograms 
per liter). Iron will not be precipitated by phosphates if the iron is 
chelated. This is because the binding constants of chelated iron are so 
much higher that those for the oxyhydroxides of phosphate (many orders of 
magnitude). Phosphate is a macronutrient and as such is needed in large 
amounts by aquatic plants. In natural systems phosphate is obtained 
exclusively from the sediment by the roots. If you have a fertile 
sediment you should NEVER add phosphate to your water (unless you have a 
large number of floating plants ... and even then the fish should supply 
all that is needed).

Dr. dave