Re: Red algae and PO4

[Thomas Barr <tcbiii at earthlink_net>]

> I've started having a small brush algae problem too and would like to
> try adding PO4 as well but none of the posts have indicated how much
> to add (I have a 10gal tank, but a standardized measurement would be
> ideal).  Can anyone suggest how much to put in the water?  As I have
> access to a fair number of chemicals (other than enema treatments!)I
> would also appreciate suggestions on the best form of PO4 to add.

One to two drops of the enema 2x a week will do it.
Or 1/2 a rice grain's worth of KH2PO4 2x week.

But lack of PO4 or excess PO4 has no effect on Red or Black brush
algae(BBA). You can try 0 to 2 ppm and it does the same.
CO2 is the main issue that will succeed in getting rid of it.
Having enough CO2 all through the light/photoperiod is the key. Not 15ppm
then 4 hours later only 5ppm of CO2 and finally at the end of the day 3ppm.
Test at both end points on the light cycle for your pH. Compare against the
pH/KH/CO2 table.

Maintain the levels at 20-30ppm and the BBA will not grow. Add the usual
KNO3, K2SO4, PO4 and traces. Reg maintenance/water changes pruning and rtry
to remove as much as you can, trim infected leaves, the plants will grow
more fairly quick.

What do you to lose doing the above? Nothing.
 
> Also, using phosphate to clear up algae seems counterintuitive (since I
> thought P is usually blamed for causing algae outbreaks), can
> someone educate me on why this should help the problem and not make
> it worse?

Well actually why would PO4 cause algae in a tank full of plants? Seems
counter intuitive to think it would not cause the plants to have an
"outbreak" of growth. Really, why would it?

If you look at tropical and subtropical lakes with plants, you find adding
PO4 causes the plants to grow faster if the system is limited in PO4.
But many lakes are not PO4 limited in FW, they are Nitrogen limited.

Much of the algae=PO4 work was done on northern lakes where plants don't
grow year round nor have such high biomass for long periods.

Tropical and subtropical lakes are much better subjects for comparing
nutrient inputs to aquatic ecosystems. They have far more relevant
temps/lighting/plant mass/growing seasons when comparing ecosystems to our
planted tanks.  

If you add a bunch of PO4 to a lake here, you'll simply get more weeds, not
algae. This has been shown in many lakes in warmer climates.
Many lakes were dominated by diatom algae at one point then shifted to
plants as the nutrients increased.

Which do you think is better able to get small amounts of PO4, plants or
algae? Answer= algae.
Do you think the amount of PO4 needed for plant growth is higher or lower
than algae? Answer = higher. Plants need and use a lot more PO4 than algae
do. 

At very high levels, it's likely you can destabilize a system. It's above
2ppm of PO4 though.

Adding PO4/NO3 etc to water is not a good thing no matter where the lake,
you get either a nasty algae issue or a serious weed problem. Lake Victoria
for instance has both problems. That lake is going to be ruined eventually
with no way to save it in sight.
  
Regards, 
Tom Barr
 
> Thanks,
> 
> Kyle