Re: KCl vs K2SO4

Paul Sears writes...
>Dave Whittaker wrote...
>	Why would you expect the UV sterilizer to affect the iron
>concentrations?  I can't see any reason to expect that.  In case
>2 the carbon filter was removed when the trace element addition

I believe that someone, maybe GB, found that UV use caused his
iron levels to fall. This makes sense in that it is known that
light speeds up the breakdown of FeEDTA in solution.
>> one should not be afraid of overdosing with potassium and
>> that one would be better off substituting KCl for K2SO4 in the PMDD.
>	Why would you prefer Cl- to SO4-- in the tank?  The plants
>can use sulphur in fair quantities, and I don't think they need
>all that much chlorine.

SO4= made up only 8% of the anions in the crypt area that Horst
and Kipper tested and Cl-, 51%. By comparison their mains water
reads 30% and 20% respectively. I thought that it wouldn't hurt
to redress the imbalance, but maybe the plants don't care.

>> Ten days isn't long. The PMDD technique works better than what I
>> had been doing. Three months will tell. I'm going to have to invest
>> in nitrate and phosphate test kits. Any recommendations?
>	I'm using a Wardley dry tablet test kit for nitrate, and it
>seems to work well.

Thanks, I'll stop in at Walmart.

>> Depends upon your chloramine levels which could be 0.5 ppm to 2.0 ppm
>> or above. If you use four times the recommended dosage for chlorine
>> written on the bottle, you are almost guaranteed to be alright. I have
>> no idea how or if it affects micronutrients.

>	I now have it.  Thanks.  Thiosulphate should work for chloramine
>in much the same way as it does for chlorine.  A somewhat higher dosage
>may be required for the same number of ppm chloramine as chlorine, 
>because the former has a lower molecular weight (51.5 vs 71, so use
>about 1/3 more).

Just a note. I read somewhere that manufactureres of dechloraminators
had set the concentrations in their products to meet the requirement
that chloramine be broken in a solution at ph 11 and not at pH 7 which
would be normal. It had something to do with an original testing. This
means that one should really use about twice the concentration suggested
on the bottle. I think that it also takes a bit more as well, although
someone contradicted me in another post on this.

Dave Whittaker                       ac554 at FreeNet_Carleton.CA
Gloucester, Ontario                  dwhitt at magmacom_com