Backyard Aquaponics
A place to discuss aquaponics

Where can I purchase Spirulina growing culture in Australia

The only source I know of is the CSIRO.
It's expensive and the strains are their intellectual property.
You can't sell it, give it away or distribute it in any way and any other strains developed from it (by you) remain their property.
All specimens must be destroyed or returned if or when you are finished with it. Pretty sure that means autoclave, not the sink.

I could be wrong but that is my understanding of it.
There are at least two forms to fill out and they might supply to non-business individuals but I suspect that best case scenario is they wouldn't like it.

But I could be wrong but that was my understanding of it.
Bummer eh?

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I buy the stuff (for consumption) from the NT.. I do "ASSUME" that the dried powder is completely sterile..

Given the MASSIVE ponds that they produce it in, I wonder how practical it could be to self-produce
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The problem is spirulina is not a native to australia. You could probably find Australian varieties if you looked in ponds etc.
I plan to grow Duckweed, which is very similiar and many varieties are native to Australia.
I have 10 acres in Kyogle with plenty of water etc and plan to grow duckweed for a high protein feed for my Ducks etc.
It can be dried but not in direct sunlight

I think you might be confusing Spirulina with Spirodela. "Duckweed" to me means genus Lemna, although it's not the only genus of duckweed. Another is Spirodela. Lemna and Spirodela are both flowering plants. Spirulina is a cyanobacterium. I doubt it's ever been called duckweed.