Re: PMDD's and nitrate

> From: Stephen.Pushak at saudan_HAC.COM
> Subject: PMDD & Nitrate concentrations
> I have a week old _experimental_ soil substrate which I have recently
> set up. I have used PMDD at a reduced dosage (but not reduced
> enough) for the last week. Recently I've been measuring various
> parameters and find that I have approximately 100ppm nitrate in
> this tank. 

	How long has this tank been going?  The implication of what is
written above seems to be that it has only been set up for a week.
If so, the contribution of the PMDD's to the nitrate there now is no
more than a few ppm.

> o monitoring NO3 regularly is critical for proper use of PMDD!!

	I think we pointed this out in the original posting on the
subject.  Monitoring nitrate concentrations isn't a bad idea in _any_
tank, and will be more important still in a planted tank, where
nitrogen _must_ be available for the plants, yet accumulation is
to be avoided.
>   Suspend the
>   addition of nitrate and probably all nutrients and micronutrients
>   in a soil based substrate until it becomes clear that the
>   plants are becoming nitrogen limited.

	I'm not wildly enthusiastic about the "mixed" approaches to
plant growing.  If you have a fertile substrate, then why add things
to the water column?  I use the water column approach mainly because it
is very easy to adjust, and I don't have to tear the tank down when
the substrate wears out.

> o in closed systems where water changes are minimal, we need to
>   be cautious about nutrient additions. These can probably be 
>   accomplished (with possible exception of Ca) by regular feedings 
>   of a balanced fish food diet (or other organic materials in 
>   fishless tanks)

	"Balanced" for the fish may well not be "balanced" for the
plants.  Do water changes, throw out plant material as it grows; the 
faster the turnover of water and plants through the tank, the less likely
is the buildup of anything.

> My advise is stick to a single method unless you know what 
> you're doing or like experimenting. 

	I agree.

> If you use small containers
> for your Crypts or other plants, you can experiment with
> much more freedom and I would encourage people to use this
> approach and share their results (good and bad).

	Is that what you were doing in the tank mentioned at the beginning?

Paul Sears        Ottawa, Canada

Finger ap626 at freenet_carleton.ca for PGP public key.