Re: Steven Pushak post

Steven Pushak wrote:
(lots of snips)
> o monitoring NO3 regularly is critical for proper use of PMDD!!

> o a fertile organic soil substrate will contain considerable
>   nutrients which are going to make nitrogen available to the plants
>   esp in the substrate itself. That substrate nitrogen will primarily
>   be in the form of ammonia which means that the plants are not
>   going to use _any_ nitrate from the water at all. 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.

There are lots of variables here. It is very difficult to determine
exactly what is already in a soil substrate. Therefore, the addition of
any fertilizers should be handled with caution. (you may very well be
adding something that you have too much of to begin with) 

> 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)

Why would the water changes be minimal? Or do you mean in comparison to
say a constantly flowing stream? Are you saying that fish food contains
all of the iron and other micronutrients that your plants need?

> o in systems where we're pumping in lots of nutrients such
>   as with PMDD, my feeling is that it's critical that a regular
>   schedule of water changes is followed to prevent build-up
>   of some nutrients.

A regular schedule of water changes should be good advice whether you
add PMDD's or not. For that matter, whether you even keep plants or not.
> o with a fertile organic soil substrate I think it would be a
>   good policy to allow the plants to grow for a week without
>   any fish and measure NO3 at that time. If an excess is found,
>   you can easily do large water changes without fear of the
>   colder temperature water adversely affecting the fishes.

Huh? Why would the water be colder?

> The lone occupant of the tank, a female platy, goes back with
> her friends tonight and I'll change a fair amount of the water.
> The plants by the way, appear to be quite happy and growing
> rapidly although 100ppm NO3 is a lot. No algae evident following
> the complete bleaching method described by Krombholz. So far
> air borne algaes have not colonized the tank.

No algae at 100ppm! Wow!
> My advise is stick to a single method unless you know what
> you're doing or like experimenting. 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).
I think that this is great advice. Especially, the part about using
containers for experimental substrates. A bad substrate in a 4" pot is a
lot easier to live with than a bad substrate in a 75g tank, and cheaper
too. By all means, experiment away. The Dupla method works, but so do a
lot of other methods. (some known and some waiting to be discovered)