David Webb wrote:
> Here's my question:  Does the term "cyanobacteria" refer to the bluish
> color that we see in our aquariums, or does it mean something else?  Many
> of us believe that cyanobacteria are capable of fixing atmospheric
> nitrogen.  I haven't seen experimental evidence that this is true, but it
> sure looks that way from my experiences with my tank.  I'm wondering if
> cyanobacteria may produce internal toxins to make it taste bad or even make
> it poisonous, but if these toxins might be a by-product of nitrogen
> fixation (CN- anions, perhaps).  I'm further wondering if the presence of
> an easier to metabolize nitrogen source such as NH4+ or NO3- might reduce
> the ability to produce such a toxin, if it exists.
> This is a lot of reaching and speculation, so I hope that some of the
> medical/botanical/microbiological types here can shed some light on my
> question.

There are many forms of cyanobacteria.  One of which is the cause of
"red tide" (in otherwords, the filter feeding shellfish injest the 
this type of cyanobacteria and the toxins that they produce).  There's alot 
of info about it on the web if you do a search.  There was some excellent 
information from Portland State University some time ago, but in my quick 
search, I didn't find it.  However, here is another summary that is
quite informative for anyone interested:


David Robinson                          The Discus Page
robinson at ichips_intel.com               http://www.ee.pdx.edu/~davidr/