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Ferrous sulphate - Miracle cure?
- To: Aquatic-Plants at actwin_com
- Subject: Ferrous sulphate - Miracle cure?
- From: Stephan Mifsud <valerandi at yahoo_com>
- Date: Fri, 27 Jun 2003 11:45:17 -0700 (PDT)
Which single compound can reduce or eliminate the
following problems, at the same time, and without
harming the fish or the plants?
1 "Brown algae" (Diatoms), Green water caused by
excessive dissolved nutrients
2 Turbid or discoloured water
3 Iron deficient substrate
4 Excessive snail population
Each of the problems can obviously be tackled
individually. eg water changes for 1, laterite for 3.
But is there a single solution to all? Here's my
A month ago I had a serious diatom "brown algae"
outbreak in both my tanks and pond, which I traced to
a high Phosphate, silicate and /or organic content in
the source well water. I introduced a phosphate
removing resin to the filter of the display tank. The
Phosphate dropped from over 3ppm to less than 1ppm.
The growth rate of the algal film diminished but did
not stop, even with 13 otos munching happily away at
it! The resin was specific to phosphate, so the
soluble silicate (which diatoms incorporate in their
cell wall) was still there. 'Not more resins!' I
thought. Too expensive for every water change. So
after some light research into methods of removing
Phosphates and Silicates I found that soluble iron
compounds (ferrous sulphate, ferric chloride) are
commonly employed to remove both Phosphates and
Silicates in water treatment plants. Well why not in
I had some ferrous sulphate (commonly found in garden
centers) so I dissolved a heaped teaspoonful in a
glass of RO table water. The Ferrous solution was a
typical green. 30 minutes before lights-out I poured
this solution into the 55 gallon tank all along the
surface. (the final concentration was roughly the same
as in effluent treatment)
At first nothing happened. Then slowly the water
became misty, cloudy and then orange in colour.
Presumably the Ferrous iron was being oxidized to the
orange ferric state. The turbidity increased until the
fish looked like they were swimming through thick fog.
They rose to the surface which is when I realised that
the oxidation of the ferrous iron must have been
depleting the oxygen availability, so I immediately
increased the surface agitation with air bubbles,
which obviously did the trick. (Next time I would do
this beforehand.) The lights went off, which was good
since the plants were not getting enough light and the
fish seemed disoriented in the 'fog.'
As happens during effluent treatment, the iron must
have complexed to phosphates, silicates, dissolved
organics (tannins etc), floating bacteria, algae and
other suspended matter to form an orange flocculate.
This in turn either precipitated on to the aquarium
surfaces or was filtered out of the water.
At lights up 12 hours later, I was happily surprised
to see a crystal clear water, even when viewing the
tank from the side. The fish were OK. The finer leaved
plants and mosses had acted as filters and were coated
in orange, but a shake dislodged this. The filter did
the rest. I squeezed out the filter wool under running
water, and siphoned the remaining precipitate off the
The coloured-dissolved organics were obviously gone
but what happened to the Phosphates and Silicates?
Tests showed that the phosphates had dropped from 3ppm
to less than 1ppm, and silicates from 10ppm to less
2ppm. A week later I happily confirmed that the diatom
films were retreating, with the help of the otos.
Green film algae had also stopped regenerating. New
leaves stayed free of any visible algae.
The other benefits
Ferric phosphate which had fallen into the spaces
between the gravel is probably acting as a slow
release fertiliser. Phosphates are at the root zone
where most needed . The ferric iron in the anaerobic
environment is also reduced back to the ferrous state
which is theoretically more available. New leaves are
a nice rich green colour.
The snails appeared to have stopped laying eggs.
Possibly the fact that Ferric phosphate is used as a
commercial molluscicide may have something to do with
I did the same with the other tanks and pond. (1
heaped teaspoonful FeSulphate to every 50gallons
water). The filter in the pond was not as efficient so
the water cleared up after 3 days, but what a change!
The slightly green water was crystal clear. The brown
algae once shaken off the leaves did not reappear.
The Source water
I have added Fesulphate to tanks of the nutrient laden
well water which clears up the problem even before it
is introduced into an aquarium, but I am still adding
it to the aquariums on a once/2week basis as an iron
source and as a water clarifier.
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