Re: PMDD Paper

On Thursday, 4 April 1996, David Whittaker wrote:

> The initial conditions of Case #1 include a UV sterilizer. That
> couldn't have helped your dissolved iron levels. In Case #2 you
> installed a carbon filter to the same effect.

I looked into the effect of the sterilizer on my iron levels ages ago.
You may recall the discussion on the subject here in the APD.
After much mucking about, I concluded that the sterilizer wasn't
having much effect at all; turning the sterilizer off didn't make any
discernable difference to the iron readings.  There may indeed be some
effect, but my iron test kit isn't sensitive enough to detect it.

> While the red beard/brush algaes seem to take off when my DIY CO2 
> runs out, that may simply be due to diminished competition with the
> plants. I wouldn't be tempted to conclude the above until I had
> better proof. It is a pretty broad generalization and there sure
> are a myriad of red algaes. 

Blatant speculation on my part (and clearly labeled as such).
Baensch and others note that red algae seems to disappear with
CO2 fertilization.  I was hoping that someone would come forward
with data from real studies.  Somewhere there is someone studying
freshwater red algaes for his PhD; would this person please step
forward?  We won't make fun of you, really we won't.

> Why do you advocate 0.1 ppm iron as opposed to 0.3 ppm?

It seems to be enough.  My Sera test kit has its first color sample
at 0.25ppm, so I'm only guessing at my actual level.  I barely show
any iron at all.  I think Paul uses the same kit.  Within reasonable
limits, a little excess iron or other trace element probably won't
hurt anything, provided regular water changes are done to prevent

> This tells me that, within
> reason, one should not be afraid of overdosing with potassium and
> that one would be better off substituting KCl for K2SO4 in the PMDD.

We picked K2SO4 because it's also a source of S, and because we weren't
keen on having too many Cl- ions floating around.  At the concentrations
we're talking about, chloride isn't likely to be a problem, but we aren't
using KCl in our own tanks and therefore we can't recommend it.

> The above question must have been addressed many times in the
> specialist literature. This is how governments prefer to spend
> their research dollars.

I keep hoping to dig up some of this literature.  Can anyone help?
The relationship between phosphorus and algae has been known for a
long time (hence phosphate-free detergents); there must be a ton
of literature out there.
Kevin Conlin   kcconlin at cae_ca   "We're Canadians.  We HAVE to be polite"
Finger as332 at freenet_carleton.ca for PGP public key.