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Re: good plant growth was Re: PO4
David Berryman wrote:
> Are you saying do not try and fix the algae problem, but try and fix the
> deficiency for the plants and the algae will go away again?
> How many thousands of different dificiencys are there out there?
Start with light. The rule of thumb is that you need 2-3 watts per
gallon of normal fluorescent light. Small tanks often need more. Large
tanks need less. Be careful that your plants don't shade each other too
much. I have a developing theory that some nutrient deficiencies may be
related to low light; they occur because the plant doesn't have enough
energy (light) to actively import the necessary nutrients.
As far as nutrients are concerned there aren't that many deficiencies to
worry about, especially if you use tap water and do regular water
changes. Very pure tap water (as in the US northwest) may cause some
problems. If you use RO, DI or distilled water then you *will* have
problems because you will have to supply correct amounts of everything
(except maybe hydrogen and oxygen).
Here's one list of essential elements, and some comments on their
supply, including their availability in common tap water.
Element Source Comments
------- ------ --------
Hydrogen water Universally present
Carbon Carbon dioxide, Always present, but needed
bicarbonate ion in water in large amounts, so can
Oxygen water Universally present
Nitrogen Nitrate ion, low levels usually present
ammonium ion in water high levels reached in
urea, ammonia and nitrate aquariums. Can be
Potassium K+ ion in water always present, but can be
potassium salts deficient
Calcium Calcium ion dissolved in water always present in hard
Magnesium Magnesium ion dissolved in water always present in hard
Phosphorus Phosphate ion, can be deficient, tends to
organic phosphorus in water disappear over time.
phosphate salts especially in hard water.
Sulfur Sulfate ion dissolved in water always present
Chlorine Chloride ion dissolved in water always present
Boron Borate dissolved in water sometimes deficient,
borax, boric acid in small amounts. Can be
Iron Ferrous or ferric ion in water, common element, but often
iron oxyhydoxides in soils deficient in
"laterite", chelated iron
Manganese Mangese ion and manganate
dissolved in water. Also in
soils, trace mix, may be
Zinc Zinc ion dissolved in water
also in soils, chelated trace
Copper Copper ion dissolved in water
also in soils chelated trace
Molybdenum Molybdate ion dissolved in water
also in soils, trace mix
Of the elements on the list we pretty much never need to worry about
hydrogen, oxygen, sulfur or chlorine. Even slightly hard water provides
all of the calcium or magnesium your plants need. Tap water supplies
usually carry enough boron.
Potassium is common in tap water, but adding more often produces
Fish feeding and fish waste provide nitrogen and phosphorus, but in a
heavily planted tank the plant demands may exceed that supply, so
deficiencies happen. Both can be added as fertilizer.
Carbon as bicarbonate is usually present in tap water, but not all
aquarium plants use that source. Even those plants that do use
bicarbonate may need very bright light to use it effectively; algae seem
to be better at it. CO2 is the preferred source, and that can be
provided by respiration in the tank or it can be added to the tank. The
carbon supply probably limits plant growth in many aquariums. That
isn't necessarily a Bad Thing, depending on the balance of other factors
in the tank.
Iron, manganese, zinc, copper and molybdenum can collectively be called
the trace metals. Iron is the one needed in the largest amounts, but
manganese isn't far behind. Some water supplies carry enough of the
trace metals that water changes alone provide a sufficient supply. All
of the trace metals can probably be provided in adequate amounts by
using a soil substrate. If problems arise -- particularly with iron
deficiency -- then its fairly common to add these metals with a chelated
Nutrient deficiencies generally have specific symptoms and can be
diagnosed with careful observation. Unfortunately when deficiencies
occur the plants are often deficient in more than one nutrient.
Further, some of nutrient deficiency symptoms are very similar. To
diagnose a nutrient deficiency you need to study your plants and
*carefully* compare them to the published descriptions of the symptoms.
Be particularly careful about whether symptoms occur on old leaves or
new leaves and where on the leaves the problems occur.
> When you
> find algae in your tank how long does it usually take you to find the
> dificiency....hours, days, or weeks?
Sometimes minutes. Sometimes months. The time it takes might depend on
how stubborn you want to be about changing your mind.
> Is there a specific group of test that
> you start with (ie. 2 or 3 first set of test then if that doesn't show
> anything go to 2 or 3 second set of test?).
A water analysis provided by your water system is the best source of
information. Bluntly, the only hobby tests that I have much trust in
are the simple pH indicators, hardness kits, and alkalinity titrations.
Expensive kits (e.g. Hach and LaMotte) work better and you can probably
ignore any result you think you got from a test "strip". It is better
to depend on your own observations, knowledge and experience then it is
to depend on a bad test.