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Peat substrates

At 02:47 AM 4/6/98 -0700, Stephen Pushak wrote:
>Toan wrote:
>> Oh yeah, Steve, how long does your substrate last? 2, 3
>> years? think I can stretch that if I start adding pmdd
>> when the plants start to show signs of deficiency?
>I suspect (but have no proof yet) that these kind of substrates will
>provide iron for many years based upon what Paul K has observed.
>Periodically I add some macro nutrients to the substrate with clay
>A more interesting question is will there be any accumulation of
>inhibitory compounds in the substrate after several months or years.
>Neil Frank has been keeping peat tanks for many years. Neil, how much
>peat do you use? How is it employed? what kind of peat do you use?

Yes, I use peat in the substrate of some of my tanks. The oldest still in
operation was set up in 1992 or so. I used a mix of peat and coarse sand in
the lower 1.5 inches covered by 0.5 inches of unwashed sand, then topped by
1 inch of washed sand. I would probably wash all the sand if I had the time
and energy. The peat is used straight out of the bag from the garden store. 

This set up worked well for the plants I tried.... especially chain swords
(Echindorus tenellus). Ironically, crypts did not initially do as well as I
had hoped... but this may be due to the water being too soft. I had used
trace elements off and on during the early years, but the slow but steady
plant growth only seemed to demand the renewal of trace elements from water
changes and the peat.  My tap water provides some iron... and without
removing detritus, the tank will eventually create its own. I can't say
whether decomposed peat will or will not be another source.  [BTW, I only
use two 40w bulbs over this 70 gallon tank. Even so, I pull out lots of
plants on a monthly basis. More light would speed up the plant growth and
might cause the system to slow down sooner].

Last year, I noticed a significant slow down in the plant growth. After
some trial and error experimenting, I finally concluded that the tank
became carbon deficient and started to inject CO2. I did considered
inhibitory substances, and allelopathic chemicals from some plants. My goal
was to get the chain swords to return to their previous growth... so I
removed most of the stem plants... no effect. It was the added CO2 that did
the trick.

I probably could have figured this out more quickly if I took a pH
measurement! (Do as I say, not as I do!!) During the early years, the peat
substrate kept the pH in the low 6's. Now, without CO2 but regular water
changes, the pH would be in the mid 7's. The minimal CO2 injection brings
it back into the 6's (with soft water, not much CO2 is needed to make this
happen). After minimal CO2 was added, the good plant growth resumed. [Note:
I believe that the slow decomposition of the peat and the low pH of the
tank water had been providing adequate CO2 until the upper layers of peat
"lost its power".] As a side note, the crypts started to flourish during
the last few years... prior to CO2 injection, but continuing. I surmise
that they did not like the combination of new peat, very acidic substrate
and soft water (low calcium). You can see a picture of this tank in one of
Karen's earliest columns in AFM. This picture was taken around the time I
started to use CO2, but it is representative of what the tank also looked
like 12-18 months earlier.

I do not only use peat and do not necessarily recommend it. In other large
tanks, I use soil in pots. In small tanks, I use a thin layer of soil
covered by coarse sand. I started to experiment with soil and peat. This
combination should be fine. Peat is nice because for one or more years
(perhaps only with soft water), you can get nice plant growth without CO2
injection. >

>Is there anyone else on the APD with peat experiences to relate (good or

It would be interesting to hear people's experiences with peat and hard
water (with and without CO2).

Neil Frank
Aquatic Gardeners Association