Re: Algae, phosphates

> From: nfrank at nando_net (Neil Frank)
> Regarding the effect of P, there was an interesting article published in TAG
> which is an English translation of one originally published in AquaPlanta
> (see TAG, V7n1). The author, Peter Peterson, slowly reduced phospahte
> concentration by adding a 0.3% solution of of iron chloride (over 8 day
> period). He reduced the Phosphate concentration to 0.1 ppm. During this
> time, he observed that some species of higher plants started to suffer and
> algae bloomed. This suggests that his algae was able to utilize phosphates
> at a lower level than some of his plants. He observes that the results may
> be species specific.
	Do you have the original reference?  I would be very interested to 
see it.  Adding FeCl3 to take out phosphate would probably take out most
of the trace elements as well, unfortunately.  They would be very prone
to adsorption on the colloidal iron hydroxide/oxide that took the 
phosphate down.
> With extra feeding he brought the conc back to 0.6 and deficiences vanished.
> He concludes that a range of P concentrations may be optimal for good plant
> growth without algae. He thinks that 0.2 ppm is too low. The article had
> many other interesting obsevations about levels and different types of
> aquarium plants and growing conditions. The above also supports Peter who
> said "Only by adding pure P over several succesive cycles will show the
> dependency of algae on P"
	Again, the "extra feeding" would provide a lot more than phosphate.
As pointed out earlier, we need experiments with only one variable!
The interesting point is the apparently satisfactory functioning of the
aquarium at phosphate levels that were very high according to some
earlier postings.  I seem to recall 50 ppb being mentioned as lots.
Kevin and I never claimed that limiting phosphate is the only way to
good results, just that we think that that is how our tanks are functioning!

Paul Sears    Ottawa, Canada