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Re: Consensus on PO4?

> Is there any consensus on the desired mg/L of PO4?
> 
> - --Stephen, who must be crazy asking this list about a consensus on anything!

Now there's a can O' worms.
It *****really******** depends on what your trying to do. I think the first
thing is to make sure the CO2 and lighting is down packed or if you even
wish to use CO2 or not. Go iron/trace limited then. If you want to try a
more traditional method try PO4 limited tank. Note, this does not mean
absent(0.00ppm) but low PO4's.

If you have high PO4 or NO3 etc you'd be well off to use CO2 at higher
ranges say 20-35ppm. Mine do not fall below this ever. I have both high and
low lighting. Lighting seems to be semi independent of the nutrient levels
but the levels get used faster is the main thing.I keep a low light tank
with high CO2 and nutrients as well. I can keep my PO4 very high by most
many standards. I can also keep my NO3's very high and have moderate PO4's.
Both together seems to bring out Green spot algae combined with Trace
elements. But I've done it without to big a problem.
You can pick which nutrient, NO3, Fe, PO4, CO2 even, each has it's trade
offs.

So a concensus based on if you have CO2 in a good amount? Low to high, it
matters far less if the CO2 is maintained at 20ppm or higher. I think  15ppm
is too low. Don't care what all the Dupla poopla says about it. I think it's
wrong.

 I've been keeping my PO4's quite high(1.0ppm or higher) in all my tanks
since moving to an area that has no PO4's. Where I used to live had PO4's at
1.12ppm.
I did not add any PO4's for the first few months after moving but kept the
other levels the same. Not too happy with the results. Reduced plant vigor,
less pearling. Some plants did very poorly.
But if your algae is under control it's alright to add it. Start low and and
watch. Let it go up to .2ppm then see how long it takes to go to zero.
Keep adding more till you have a good residual. Test it daily till you get a
feel for your tank's consumption rate. I keep mine high like my old tap. I
can go higher but why? I doubt it's going to help but in interest of a
"breaking point" I might sometime. So a reading from 0.1-0.2ppm for a PO4
limited tank and a more NO3 limited tank perhaps 1.0ppm.

A NO3 limited tank can be tough. Good regular fish feeding seems to really
help. Additions of KNO3 in light amounts works well. These would be deleted
if you had say high NO3's in your tap water or smaller water changes may be
in order. Tap waters make a difference also therefore. Many folks have too
many fish and are not willing to try this since the fish a primary thing and
the plants are secondary. But happy plants will make for happy fish IMO.
Certainly a better place for the fish in an overstocked tank with so so
plants.
I use Mic. umbrosum as an indicator in my aquariums and Crypt lingua in my
Crypt emmersed tank. Both are sensitive to lower levels of NO3.

My PO4 indicator is Eichhornia diversilfolia.
http://www.sfbaaps.com/gallery/display.php3?barr/barr_02_02.jpg+Ludwigia%20i
nciliata,%20perhaps%20one%20of%20the%20most%20beautiful%20of%20plants

It's not inciliata:) That's the E diversilfolia. Try to get it to look like
that without any PO4. You won't do it.

 Color of many red plants is intensified by low NO3 so I get good colors and
fast growth using this method. But it has trade offs like all of the
methods.

You want consensus? Test it. Decide on an approach. Try one then try
another. See what happens to plants and algae. That's really all I've been a
doing all along. Approaches are something I really like about this hobby. So
many ways to skin that cat that I'll never get bored:) Ran out of plant
species awhile back, on to algae. Bacteria will get it next:)
  
FWIW, 
Regards, 
Tom Barr