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Re: Aquatic Plant Food 20-10-5

>From: Kevin <kevin16 at home_com>
>Subject: Re: Aquatic Plant Food 20-10-5
>Ed was kind enough to reply:
>> 20-10-5??? WOW that's HIGH in nitrates!  I would strongly suggest to NOT
>> use that in an aquarium unless there's a nitrate deficency, i.e. 0  Then
>> monitor it closely as this can and possibly WILL cause the nitrates to
>> skyrocket.  Do a test, take a gallon of bottled watter, and test
>> nitrates, then put the recomended amount in then check it again in about
>> 30 mins and compare the results :)  Then ask yourself if you want to put
>> this in your aquarium,  if you have fish then you probably do not want
>> to add nitrates.
>> Under most conditions you can add trace elements and be on the safe side
>> (presuming you have fish in the tank)
>> Ed
>Thanks for the advice.
>I did a test similar to what you recommended. I put 1/8th of a tablet in
>a gallon of my aquarium water. The tablets are quite large. 1/8th of a
>tablet is the size I was thinking about using near each plant. I tested
>the water before and the nitrate was zero. After letting the tablet sit
>in the water for 4 hours I gave the water a good stir and tested again.
>Again the nitrate level was zero.

First, it is very misleading to say that "possibly WILL cause the nitrates
to skyrocket" Maybe if used in a 2 gallon tank, but not in a 250 gallon
tank. Final concentration is totally dependent on the amt of material used
(in this case, some percentage, like ~20% of tablet weight) AND the amount
of water in the tank AND if placed in the substrate, insulated is the
fertilizer from the water column.

>How to explain? These are supposed to be slow release tablets. Maybe I
>would have seen a rise if I had let it sit longer. Also, you might note
>from my original post that the bottle says that about 1/3 of the
>Nitrogen is Urea Nitrogen and 2/3 of the Nitrogen is "Water Insoluble
>Nitrogen." So maybe 2/3 of the Nitrogen never dissolves to raise
>nitrates. I'm no chemist so perhaps I am wrong to think that a Nitrate
>test kit with measure the form of Nitrogen being released.

I am not familiar with the chemistry of the nitrate test, but the test
result described above might not respond to urea. It also might not be
dissolving because of the clay coating. Try stirring it. Even if it showed
measureable nitrogen or nitrates, the 1/8 tablet in 1gallon would have to
be scaled up to 1 tablet in a larger quantity (in this case, 8 gal). Even
so, the use of these tablets or any other source of N-fertilzer could and
probably should be applied in smaller quantities.

>Anyway, I'm eager to hear any more suggestions you or others have
>regarding this product. 

This product has been on the market for over 30 years. It may have been one
of the first aquarium plant foods, but it has too much P and not enough K
in proportion to the N. While it may be better than nothing to correct a
N-P deficiency (if you know that you have this), there are better products
available today as mentioned many times on this list. Assuming that the
fertilizer can leach into the water column, two other possibilities are
Jobes for ferns (16-2-6) and regular jobes (13-4-5). Both of these provide
the NPK in the more desireable ratio of (5: 1 :2.5).  I have read that
people like to limit total P and use the first, but I once found that Jobes
Fern provided too much N to a dense planting of small plants.