Re: Nutrients vs. algae

["S. Hieber" <shieber at yahoo_com>]

Jeremy White said:

> It is my theory that many who think they are having
> success by limiting PO4,
> really are not.
> 
> People with either a large fish load, or inadequate
> lighting have much more
> difficulty depleting the PO4 then I do.  They think that
> they have limited
> PO4, when in fact enough enters the system through
> regular feeding that
> their PO4 never really hits absolute zero.  Thus, they
> think that they are
> limiting, when perhaps they are not.
> 
> My PO4 on the other hand, quickly hits absolute zero in
> about 4-5 days after
> I dose it.  I don't have very many fish, and I have a
> huge amount of plant
> growth.
> 
> I have seen SEVERAL posts that say that PO4 should never
> hit absolute zero,
> and that some people have had much better success with
> adding small amounts
> of PO4.... which also backs this theory up.
> 
> Also, I should add that my water parameters (PH, KH, GH)
> are almost exactly
> the same as yours.  I have very soft water, as I keep
> discus.

I want to limit my PO4 to about 0.7 ppm or at least not
more than about 1.  I don't want it to be unlimited.  But
there's a big difference between limiting PO4 and
eliminating PO4.  I ran into a guy in ThatPetPlace that
wondered why his plants slowly died over a few weeks and
despite repeated new plantings, never grew -- among other
consternations, he was using a very large chemical
phosphate remover.  I suspect lack of PO4 might have been a
problem for his plants.

Even with heavy feeding (and without chemical phophate
absorbers) the addition of PO4 might be useful.  I have a
heavy fish load and heavy feeding.  Still, I actually need
to add PO4 (I add about a 1/32 of a tsp after the weekly
50% water change in a 150 gallon tank.  I happen to have a
1/32 tsp. and that seemed to fit Tom's recommendation of
"about a pea sized" amount.)  This small addition brings
the mix of old and new water up to a useful level right
after the water change.  

Although the plants undoubtedly consume PO4 over the course
of the week, the PO4 starts to climb slowly over the course
of the week due to feeding.  But the PO4 is still at a
reasonable level by the next water change is due (0.7-1.0
ppm).   I do the same small dosing with KNO3 but not on a
regular basis.  Some weeks more NO3 is needed, other weeks
not.  I don't need to add much in a big tank because the
food is providing most of the PO4 and KNO3.  The dosing
just fine tunes.

I use LaMotte test kits as the basis for when to dose --
well, mostly in the beginning.  After things became very
stable, I came to rely less on testing and more on other
observations.

I didn't discover this this stuff -- I learned it from Tom
B.  Search the archives about algae, dosing, and Tom Barr. 
I happen to know there is some really helpful stuff.

Scott H.

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