K2O isn't a form of K that is commonly used. It's just for
measurement/comparison purposes. Every Potassium fertilizer will
list it's contents in the equivilent amount of K20.
Commonly used forms of K used for planted tanks are KCl (Potassium
Chloride), K2SO4 (Potassium Sulfate), and KNO3 (Potassium Nitrate).
KNO3 is used when extra nitrate is needed, which is common in very
high growth situations where CO2 injection and high light are used.
> The HCL is there to reduce the pH of the solution. YOu
> will need a pH meter when preparing this mixture so you
> can be certain the pH is around 7 (+/-1)
No, as the author of the recipe mentions, the HCL is there simply to
prevent the growth of fungus and may be omitted if the mix
is kept in the refrigerator. I've never added HCL. I just keep the
bottle in a cool dark place, and I've never had a problem.
> Most tanks rarely have a shortage of nitrates and
> sulphates as well as phosphates. All these anions are
As I mentioned, in high growth situations, nitrate is often
deficient. When the nitrates are depleted, plant growth will
slow down and leave the other nutrients (primarily phosphates)
available for the algae.
A target level of 5ppm Nitrates is commonly used. In most PMDD
recipes I've seen, KNO3 isn't added to the mix, but rather dosed
seperately, since the amount needed will vary greatly from tank
to tank.
For articles about planted tanks, and lots of pics of my planted
rainbow tanks, check out http://www.csd.net/~cgadd/aqua
-- Chuck Gadd