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Re: PO4 limited in FW/references/evidence

 Doug wrote:

> Tom:
> 
>> In _most_ natural FW environments.
> 
> I'll have to take a look at the aquatic ecosystem literature, that's
> a great idea.  One thing is that tanks are not link regular
> freshwater environments, so I  wonder to what extent they're really
> comparable. 

I always ask my self this question when looking at references: Does it
really support what I or the writer is trying to say here? Many times I find
it does not or only very weakly. Perhaps out of 4-5 references in a number
of papers, one might be close and of good relevance. Better work, text etc
tend to have a much higher ratio. Personally, I strive for this. Sometimes
the literature simply does not exist that is pertinent.

 Sometimes a good analysis can apply a reference to shed new light on some
very different research. That's cool. That's a wonderful skill to possess.

But sometimes it goes nowhere. One cannot address everything all the time
but coverage of the main points and response to critique is not a bad idea.
At least try and acknowledge the assumption(s). Leave no stone unturned. Ask
if the assumptions are valid and discuss them amongst cohorts. We have done
that for awhile here and privately. I feel this has been very productive.
 
I have a difficult time relating an artificial lab system to the natural
world. So would any scientist. It's still done none the less. Is something
better than nothing? Hummm.....
But taking a series of lab, field treatments, and natural system test
controls and compiling these together you can analyze systems pretty well to
undercover the mechanisms that cause the observed variations. Well
hopefully, sometimes after 5 years you don't get any decent data:)

Still compiling this amount of data to argue something for a hobby like
aquatic plants is ...well low on the priority:)

It's interesting to consider artificial CO2 since the world is going to have
higher levels no matter what we do at this point. How bad is up to us now
and in the near future. This is something that needs to be address in a big
way.

 I find Roger Miller's results with the vallisneria
> interesting, to be sure. I suppose that there's a lot of experience
> out there that hasn't been codified, but that suggests that this idea
> isn't totally bunk.  Someone would have noticed by now if it had no
> effect since I suppose many of you all have some kind of phosphate
> kit.

I've been testing PO4 for about 4 years(Lamott/Hach Kit) and did a number of
what I call "practical dirty experiments"(not a real experiment). Basic
premise is will it show a noticeable difference to the common user. Will it
help? Does it cause algae as many had said prior? Where's my algae then?
Will other people be able to duplicate my results?
The answer is pretty obvious now.

The notion is to try, within reason, to keep a set of levels within a
range(rather than strict adherence) and manipulate a single variable at a
time. You manipulate the variable till you get a destabilizing effect (algae
occurrence/fish stress/beyond the range of normal levels thought to be
beneficial (Say 2.0ppm for PO4 for instance)). There is no real control,
folks are simply not going to try that or set it up.

Through this, one can find a number of practical results. It's not difficult
to maintain "a range" for the set points. The state variable should be
looked at carefully though during the test run. Most runs can be done over
3-4 weeks time periods.

Low CO2 seems to cause a number of poor results when looking at NO3 or PO4
etc. Traces are also blamed like PO4 for algae. I add more than anyone I
know. I also added more PO4 and had higher levels of that as well. Now there
are folks adding PO4 on a regular basis. Are traces next? Perhaps. It was
taboo to add PO4 in the not so recent past.

I cannot use Fe testing levels in the water column due to many different
issues with the iron testing protocol, timing of when the sample it taken
after addition of iron for the test, what is bio available etc. I just use
the amount vs the volume per unit time. This is somewhat consistent and gets
around bad test kit. It doesn't address uptake but neither does a test kit.

Heavily PO4 dependent plants include E diversifolia/azurea, many crypts
respond very well, Riccia does very well, most faster growing weeds, deeper
greens, a greater amount of pearling, moderate to slight increase in mass,
less algae presence. Reaction to additions take place in about 30 minutes to
3 hours. You can tell after you add it and it's not the algae, it's the
plants that are responding. Some want to argue that substrate alone is
removing much of the PO4. I tend to doubt this. You would see some leveling
off of uptake there after a few years. I have not seen this. A simply way
around it is to use non rooted plants and no substrate. Haven't done this
yet.
Regards, 
Tom Barr







> 
> Doug