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Re: Nutrients

>Date: Sat, 26 Jul 2003 14:43:23 -0400 (EDT)
>From: Paul Sears <psears at nrn1_NRCan.gc.ca>
>>  I have a peat substrate tank that grew wonderful plants for over 5 years
>> without injecting CO2. I assumed this primarily was from HCO3 conversion,

As Paul said, by reducing the KH.

>You would have to keep on adding bicarbonate and peat.

With water changes, I would be adding more HCO3.  I also had to add a
little CaCO3, for depleted Ca levels but which also provides more HCO3.

  I think that
>almost all of it would have come in in the ordinary way, from the air
>and fish.  One could get an estimate of the total amount of CO2
>from a given amount of peat by doing a titration, I suppose... :)
>> in addition to supplemental CO2 from the slow decomposition of the OM.
>Yes, but surely not all _that_ much of it disappeared over the years...?

Thats what I would have thought too, but over the years, peat migrated thru
the substrate. Initially, it was all concentrated in the lower half. Then
the neat dividing line of a dark lower substrate and light coarse sand
substrate was less apparent when viewed from the front glass. In some
no-filter-peat-tanks, I have seen the peat completely float up and sit on
the surface. With water movement and filtration in my 70 gallon tank, the
peat may have been filtered out over the years. I lightly siphon the top of
the substrate once every 3-4 years, so this is another way to remove some
peat. There is still peat in the substrate, but it may be coated with other
junk making it less "active." In any event, small amount of CO2 injection
became necessary to restore the plant growth that had slowed over a period
of what I seem to remembers as 3-4 months, after ~5 years of no added CO2. 

>> Because I have soft water, I had to be careful to not let my KH get too
>> low.  When growth slowed after the first 5 years of relatively effortless
>> success, I added pressurized CO2 and everything has been fine since
>> (another 6 years).  Same substrate, albeit with less OM.
>> Neil
>> PS. I also did water changes and added traces, etc. :-)

>How much water did you change, how often, 

30% every 2 weeks,

>how much KH was in the replacement water
  total hardness (expressed as CaCO3) is 24ppm, (as reported by my water
supplier). Some of this is from Mg.

From a tap water analysis result I pulled out of my files:
   hardness, 35ppm and Ca= ~10ppm 
   total alkalinity (which I assume is CO3+HCO3) =~20ppm

 and at what pH did you operate?. 

not sure (because I hardly ever test, and it was 6 years ago), but I seem
to think it was in the low 6's in that tank before I added CO2.

 If you were
>adding soft water (as implied above), I rather doubt that the total CO2
>added this way can have been all that great.  Did you do KH measurements
>on the operating tank?  I'd be interested to try to work a few things

>I've never used peat.  Does it reduce measured GH _and_ KH?

dont know, i didnt test. But, as I said, I had to add CaCO3 when Val
stopped growing, so I have to assume it was because of the depleted Ca. But
this depletion in my densely planted tank could have easily come from the
plants which are fighting for the meager 10ppm which comes in with the tap