"Graham Ramsay" wrote in message ...
"Bill Kirkpatrick" wrote
You're preaching to the choir, perhaps reply to the post
that made the claim. Everyone ends up inoculated with BGA,
and BGA doesn't care about NO3 - it will fix it's own nitrogen.

There are a great many types of BGA. As I understand
it they do not all fix nitrogen. Do the types found in freshwater
aquaria fix their own nitrogen? If so what types are they?

Thanks

I've only seen two genera, Oscillitoria is the 99.99% genus we find in
our tanks, one very nasty tank had Phormidium.

These genera need to possess heterocyst in order to fix N2 gas, no
heterocyst, no N2 fixation. Heterocyst are clearly and easily spotted
under a microscope.
A number of german aquarist also reported the same thing.
See some old post off the APD.

Regards,
Tom Barr