re:Aquatic Plants Digest V1 #2

> From: Erik Olson <olson at phys_washington.edu>
> Date: Thu, 6 Apr 1995 08:23:06 -0700 (PDT)
> Subject: Crypt rot

>Starting about 2-3 weeks ago, virtually ALL of the brown "wendtii"
> began to melt; I went on vacation and now that I'm back it's completely gone
> except for a few newer shoots.  More of the green "lutea" seems to have 
> survived, planted in the same area & mixed with the brown "wendii".
> Here are some things I have changed to the tank that might have brought 
> this on:
>   * Removed a lot of pygmy chain swords and replaced them with 3 species of
> Anubias about a month ago.
>   * Uprooted lizard's tail (Saururus).
>   * Added 2 or 3 rhizomes of Crypt pondetifolia (sp?) in another part of the
> tank.
>   * Added several bunches of Ammania sp.
>   * Added an Echinodorus osiris (which was doing well initially but has
>     seemingly stopped now).
>   * Lowered tank temperature 80-75 F approx. TWO months ago.
> What has NOT changed much is nitrate level, which I've checked weekly.  I 
> also do regular water changes of 4-8 gallons per week or two.
> So... I would like to learn more about Crypt rot.  Is this a seasonal 
> thing, perhaps triggered by changes in our water?  Is it a reaction to 
> other plants?  Given my situation, I don't think it's due to a change in 
> macronutrient level (which most of the books suggest) as that's been pretty 
> constant.  I have noticed in the past that SOME of the crop will die out 
> and come back, but I've never had such a mass suicide as this.

I've read books that say crypt rot is caused by excess nitrogen, that
it is caused by excess iron, that it is seasonal, what have you.

I don't think it is any one of these factors, but it's probably a combination.
Isn't this the time when the water supply folks flush out their pipes by
adding adding chemicals?  Dis the rot happen right after a water change?