"Shawn" wrote in message
...
I'm not a chemist. Can someone tell me what KNO3 is and where I can buy it
?

KNO3 is potassium nitrate. The common name is saltpeter. It's a white salt
(visually indistinguishable from ordinary salt). You can get it at hydroponics
stores. To keep your plants happy, you should aim for a nitrate level around
10ppm. Get a test kit to see what nitrate level you have currently though
before throwing in any more -- in large concentrations, depending on
fish species, somewhere around 50ppm, nitrate becomes toxic. (Some fish
are more robust than others and will tolerate 100ppm, but don't ask me
which -- my tank never gets above 15ppm :-)

If you weigh out 162 grams of KNO3 and dissolve that in 1 liter of water,
you get a stock solution such that 1 ml of the solution in 100 liters of water
will raise the NO3 level by 1ppm. So, if you have a 500 liter tank at 0ppm
KNO3 and you want to bring it up to 10ppm, you add 50ml.

Dosing isn't that critical -- if you accidentally add twice as much as
intended,
you still end up not killing anything, so measurements within 20% or so are
good enough.

You can work this into US gallons: 4ml (well 3.8, really, but that's close
enough)
of the stock solution into 100 gallons will raise the KNO3 level by 1ppm.
The solution lasts indefinitely, no refrigeration needed. Label the bottle as
poison
though! I haven't tried, but I suspect KNO3 would taste awful, and I have no
idea
what would happen if someone swallowed it -- it may well be toxic.
Left-over soda bottles with their labels still on are probably a bad idea...

Cheers,

Michi.
--
Michi Henning Ph: +61 4 1118-2700
ZeroC, Inc. http://www.zeroc.com