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Re: sterilization of peat for emerse culture

I would never bother sterilizing peat which is going into an aquarium.
Aquariums are never ever sterile considering that they are open to the
air and contain animals and all kinds of sources of bacteria. When you
are growing something in a moist, enclosed environment like a jar, you
don't want any mold or mildew spores in it. Peat fresh from the bag
should contain little mold but mold spores are everywhere in the air
except in an extremely dry environment. 

If you are growing tiny bits of plants (tissue culture) in agar nutrient
solution, you must ensure that there are NO molds at all or the culture
will be overgrown within a week or two. On the other hand for emerse
culture absolute sterility is not a necessity; you just don't want to
have a big growth of cyanobacteria on the surface of the damp soil. Mold
is probably not a big deal since molds are important in the rotting
process in soil. Mold and bacteria are ubiquitous in natural soils.

Peat, clay and soil are never used for tissue culture; only sterile
nutrient mediums such as agar.

You can get the temperature in a microwave up to over 100 C easily or
even better, in a pressure cooker and that should be enough to kill
molds. Aquatic plants can still have mold, bacteria and algae on the
surface so it should be rinsed well and sterilized too for tissue
culture. For emersed culture in a humid environment, I'd probably bleach
Crypts and probably try a very light bleach solution with fine leaved
plants. Sterility is not crucial because you only want to get the plant
to grow enough to get a sample which is free of algae for a second
culturing. You take that sample from the growing tip after the plant has
grown an inch or two.

Biplane10 at aol_com wrote:
> Hello Steve,
> I appreciate your informative post. You mentioned you were going to sterilize
> your soil mixture in the microwave. I have sphagnum peat I purchased at
> garden supply which I intended to use in the aquarium. Up to this point I've
> purchased peat specifically made for use in aquariums, but it's significantly
> more expensive. I was deliberating on which method or even whether
> sterilization was needed, as it is produced by composting, which would
> produce heat in the process. I usually tend to err on the side of caution,
> and was thinking of heating in an oven. How do you monitor the temperature in
> the microwave to be sure you are reaching adequate heat/time for
> sterilization? If you could provide more info, I'd appreciate it.
> Thanks in advance,
> Sylvia
> << I plan to make a mixture of sphagnum peat, garden
>  soil and some pottery clay and sterilize it in the microwave.   >>

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!