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RE: Basic fertilizers - commercial



Andy Moore asks about the Potassium and Magnesium content of commercial
fertilizers

>Is it safe to assume that a commercially made basic plant fertiliser (one
>without the micro/macro ? nutrients that are easy depleted) contains
>Potassium/Magnesium etc. ?? Most basic aquatic plant fertilisers that I
have
>come across in the UK (not many) do not list their ingredients.

Have you tried contacting the manufacturers and asking if their products
contain K or Mg? More and more companies are willing to give this
information, especially on a one-on-one basis to individuals. It certainly
never hurts to try.

>If my existing water is eg. low in Potassium (per a water report) can I
>safely assume that a basic fertiliser will correct this ?

It has been my experience that it is only safe to assume that the sun will
rise in the morning. Assume anything else at risk of great personal
dissapointment <g>.

Neither K or Mg is likely to cause much of a problem if in present in a
slight overabundance, so if you add either you won't be endangering either
your fish or your tank (in moderation, of course). For an easily obtainable
Potassium source, go to your local pharmacy (I suppose that in the UK you
say "chemists") and pick up a bottle of Potassium Gluconate tablets. You'll
find them in the dietary supplements section, generally next to vitamins.
Make sure that there is nothing else (eg., sugar or fillers) in the tablets.
They are a cheap and easy way of dosing Potassium. Target range for K is
generally 5-10 ppm (mg/l).

For Magnesium, you could use epsom salts, also available from your local
drug store. Just dissolve about a teaspoonfull in a glass of warm water and
add it to your tank. It helps to have a good Hardness Test Kit, one which
can differentiate between Total Hardness, Calcium Hardness and Magnesium
Hardness. Both HACH and Seachem make such a kit. Using the test kit, you can
determine how much Mg is in the water to begin with and so you have an idea
of how much you might need to add. The test kits generally read in
"equivalents of CaCO3", but don't sweat it - check the archives for tons of
info on what that means.

The big plus with epsom salts is that after you have dosed your aquarium,
you can use the rest of the epson salts in a nice big tub of hot water and
soak your cares away.... you must get tired lugging that tuba around <g>.

James Purchase
Toronto