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Re: sulphur odor

Scott Z wrote:

> My substrate is about half to three quarters inch clay
> cat litter, topped with about two and a hlaf to three
> inches of sand topped with around half an inch or more
> of flourite. THe odor only comes when I pull a plant
> out.

The odor usually is caused by sulfur-bearing chemicals that form in the
absence of oxygen.  I usually associate it with hydrogen sulfide, though
I don't think that is always true.

I don't think that strong sulfur odors are a common or persistent
problem for most of us.  My guess is that they'll go away as the
substrate "breaks in" and as plants extend their roots into a larger
proportion of the substrate.

If you used fine sand for the sand layer in the middle of your substrate
then that may be part of your problem.  Fine sand doesn't always cause
problems, but every now and then someone runs into something.

If the problem does persist, then you may want to redo your substrate.

Scott H wrote:

> Wouldn't the odor be sulfur dioxide (possibly sourced from potassium
> sulfate)?  In any event, wouldn't it be an indication of aerobic conditions
> down under?

Sulfate is the usual form taken by sulfur in aerated water and even in
most anoxic water.  Sulfur dioxide is a relatively reduced form.  You
don't find sulfur dioxide in solution because it reacts in water to form
sulfite and then with oxygen to form sulfate.
In natural water sulfate reduction occurs only after nitrate, manganese
and iron have already been reduced.  The usual reduced form of sulfur is
either elemental sulfur or sulfide, not sulfite.

Roger Miller