Aquatic Plants Digest V6 #209 / Ferrous sulphate - miracle cure?

[Stephan Mifsud <valerandi at yahoo_com>]

> It's unlikely you can beat diatoms with Si removers,
they can live in very
> pure water and are often found in such locations.

Is it safe to generalize about all diatom species? Why
do reef aquarists use Silicate removers to control
diatoms?


> PO4 has been shown here and numerous other research
studies that it does not
> cause algae outbreaks __when growing plants__ are
present.

Can we assume the reason is that the plants are
depriving the algae of their share? If so, what
happens when the Phosphate levels exceed the plant
requirements...won't the algae now have access to the
excess? Why do we aim for a Phosphate content of
0.4-1ppm and not more? After all, all I was aiming at
was to get the Phosphate from 3-4ppm down to this
level. 

Appr. 10 years ago I cleared the pond of a green hair
(?) algae problem by reducing the pH of the water
using Phosphoric acid. Shortly after all the plants
were covered in a brown dust, which at first I thought
was mulm churned up by the fish, but then, under the
scope, saw they were diatoms . Phosphate levels at
that time were v. high due to the acid. Coincidence? I
remember that a couple of water changes (phosphate
free then) solved the problem.


> The organic content.........well if it's got NH4 by
products or high
> Nitrogen generally, you have found the source of the
tap water problem.
> Running/adding carbon etc will help this.

Nitrate problems are very low. I have to add it daily
to try to keep it in range. I don't think that's the
problem. BTW Can't algae utilise disolved short
chained organics? 


>Adding PO4/Fe etc to a densely planted lake/pond/tank
will
> cause algae, the plants will grow more, but if
there's around 50% coverage
> on the lake, maybe more on smaller systems, you
should not see algae
> increase. 

Sorry, can't understand this.


> So what happens when you uproot a plant? What
happens to all that mulm?

Why have a mulm problem? I use a scissors to cut off
the roots before leaving the substrate, just leaving a
couple of inches on the plant. The rest stay in the
substrate.


> Plants will take in PO4 rapidly from the water
column, this can be measured.

All types of plants? Will a tank composed of 90%
Anubias, moss, ferns, echinodorus and crypts utilise
alot of Phosphates rapidly?


>Resuspension of that PO4/Fe from a reductive
substrate will cause a bloom if
>the water is PO4 or Fe limited which is likely the
case if it cleared the
>problem up over the long term 

How can the phosphate be resuspended if it is combined
to the iron? And even if it can, won't it recombine
and precipitate? And even if some of the iron has been
used by the plants and there is a phosphate excess,
why not just add more Ferrous sulphate?
How can it be Fe limited? - I added not removed the
iron. I also add chelated iron.

So, are you suggesting that a high PO4 level can be a
cause of a bloom? - in the right circumstances?

If so would'nt that partially explain why the Ferrous
sulphate worked. ; )   


> Regards, 
> Tom Barr

Regards
Stephan

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