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[APD] RE: Notes on K+ /Dirk's tank

You must consider that a combination of things can happen here, one is the
plant species in question, Ammannia, Eustralis etc act funny, , unknown K+
levels(and other nutrient issues beside K+), and other factors we have not

But many folks report that the 3 plants have issues, not others. Some
plants will certainly not fit the typical conditioins recommended. Finding
them and making sure what it is they dislike or do not dislike is a key. 

As far as figuring out what a plant assimilates a week/day, you can use the
relative proportions of N:K+ to estimate a general range of K+ needed per
Say if you can manage 3ppm of NO3 per day, divided by 4.4= ~0.7ppm of N and
since the ratio of N:K+ is roughly 1.5:1, roughly 0.4-0.5 ppm a day of K+
should be enough, I would suggest a little extra though just in case.Some
plants may need more, less etc.
You also need to consider the NH4 sources that you cannot meausre for
sources of N so that would add to the K+ overall tank demand. So you might
want to say 1-maybe 2ppm max a day of K+ in the maximum growth in a tank
with good light. So 10ppm max or so would be the upper limit with some
extra error built in.My typical advice comes in at about 10-almost 25ppm a
week depending on the NO3. While a target range is good, as long as you do

50% weekly water changes will prevent build up, see past post on the
relative ppm concentrations that are influenced by water changes.

Basically, for that 75 gal, you do not need to add K2SO4 likley.
I'm about to say that folks generally don't need any K+ supplementation at
all with K2SO4/KCl if they use KNO3 as well.

Tom Barr


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