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.


Kelly Duffie
Cypress, TX