Kelly- Go back and re-read the excerpt of my blog post that you cited. You will see that it states that Nitrobacter is stimulated, but Nitrosomonas is inhibited when levels reach 0.20 ppm. If the bacteria are active, then bioconversion is occurring. And yes, some aquatic plants have the ability to absorb many toxic agents. The key here, as stated in the article that you posted, is the 15 days. A lot of damage can be done to the food chain/web in hours. It is quite possible that a toxic level might not be reached in a large pond from the low input indicated in this thread, only testing can determine that, but pond owners can only benefit from knowing the facts concerning Heavy Metals and other pollutants and the possible adverse impact they may have on the health of their pond.
Originally Posted By: Kelly Duffie
Instar - I read your blog, but sense that it contradicts your previous statement.

"The only organisms that have not been discussed are the bacteria, in particular, the nitrifying bacteria. The results of studies on the toxic effects of Copper are quite surprising. Copper and Zinc appear to be the least toxic of the metals tested. Copper, at low levels, actually stimulates activity in both Nitrobacter and Nitrosomonas. At levels up to 50 mg/L the Copper ion has no toxic effect on Nitrobacter. Instead, the stimulatory effect is readily apparent...... Apparentlly. at 50 mg/L Copper has not reached the dross-over point where a chemical shows neither stimulatory nor inhibitory effects.(sic) This, unfortunately, is not true of Nitrosomonas. Growth of Nitrosomonas is greatly inhibited (about 60%) by Copper concentrations of .20 ppm."

So, if I correctly understand your blog, low levels of copper stimulate the activity of Nitrosomonas, but also inhibit their growth. Is the term "activity" considered synonymous with "nitrite conversion"?

In any case, in 25+ years of working with copper-algaecide treatments, I've never encountered a fish-kill that was related to copper-toxity (except one such case in which the result was intentional, and wasn't my call). Treatment-induced DO-crashes, although relatively rare, are a different story - and not strictly related to copper-algaecides.

Granted, it's possible that aquatic invertebrates might be temporarily impacted by copper-based treatments. But, I've never observed a copper-treatment's sustained impact on aquatic invertebrates. Then again, I have no dealings with koi-ponds.

On a side note, shown below is an excerpt from an article that I found interesting.