"Dances With Ferrets" wrote in message
om...
Heya folks... anyone got any ideas for cheap sources of bioavailable
potassium for a heavily-planted 50-gallon tank, along with approximate
recommended doseage? Someone told me potassium permanganate, but I
have serious doubts about this.

Potassium permanganate is a strong oxidizer and not suitable. I'd suggest
Potassium nitrate (KNO3), which you can get at any hydroponics store.
Dissolve 162g of the salt in 1 litre of water. 1ml of the resulting stock
solution
will raise the NO3 level of 100 litres of water by 1ppm. If your tank is
heavily planted, chances are that you will have to supplement nitrate anyway,
and the plants appreciate both the nitrate and the potassium.

If you need to dose phosphates as well, try potassium dihydrogen phosphate
(KH2PO4). You can also get it at hydroponics stores or at laboratory supply
shops. Dissolve 14.2g of the salt in 1 litre of water. 1ml of the resulting
stock
solution will raise the PO4 level of 100 litres of water by 0.1ppm. (If you
are having trouble weighing 14.2g, ask a friendly pharmacist for help, or
make it 142g into 1 litre of water. The take 100 ml of this high-concentration
solution and top it up to 1 litre, and you now have the 14.2g stock solution.)

Shoot for around 8-10 ppm of nitrates and 0.3-0.4 ppm of phosphates in
your tank, and watch the plants take off :-)

BTW -- someone recently posted a useful link for dosing nitrates and
phosphates. Here it is once mo

http://www.xs4all.nl/~buddendo/aquarium/redfield.htm

That's a nice tool to use after a water change when you need to work out
how much nitrate and phosphate to add in order to replace the removed
nutrients.

Cheers,

Michi.

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