re: PMDD questions

Ages ago, Paul Sears wrote:

> > The weird thing is every time I do a
> > water change I suddenly see a burst of activity in my plants, i.e. the
> > plants release oxygen bubbles like crazy.  This, to me, indicates a
> > nutrient deficiency but I can't figure out what it could be.   Any
> > idea's???
> >
> 	The same thing happened in Kevin's tank, so we tried a couple
> of experiments.  It isn't a shortage of nickel or cobalt.  It now occurs
> to me that one might use up all the calcium in soft water, so we should
> try that too.  If I remember correctly, Kevin tried NaCl, so it isn't
> either of those ions, either.

...And it's not Al+++, but that was a long shot.  I was able to induce
some bubbling by adding a phosphate pellet, and thought perhaps that
as part of the water treatment process a little phosphate was sneaking
into the tap water.

> 	The water going into the tank would be expected to have a fair
> bit of dissolved gas, if it came from a cold water main, but I wouldn't
> expect it to be enough to produce the sort of effect Kevin regularly
> saw (and still sees, Kevin?).

With the revised PMDD formula, the plants are pretty much bubbling all
the time now.  However, the bubbling does increase quite a bit after a
water change.

The original poster mentioned an iron level of 0.5ppm.  This is a
little high; perhaps what's happening is that the concentration of
some other trace elements are getting too high and inhibiting
photosynthesis, but I think it's highly unlikely that the typical 25%
water change would reduce the concentration of some element enough to
start up photosynthesis again.
Kevin Conlin  Montreal, Canada  "We're Canadians.  We HAVE to be polite"
Finger as332 at freenet_carleton.ca for PGP public key.