Copper Treated Rock

[Justin1989]

I have had my tank up and running for over a year now, probably have around 120 lbs of live rock bought from liveaquaria, and fish stores around the area. Come to find out today rock we bought (maybe 15lbs) from a local fish store was copper treated and no one ever mentioned it till today. Over the past few months I have lost hermits, snails, emerald crabs, and sea hares. I still have some snails and hermits around along with a sea cucumber and my starfish however wasn't sure if this was the cause of me losing 15+ inverts. My main question is can I add inverts at this point if the rock was added months ago? Or is this rock basically deadly till its removed?

[HighlandReefer]

It may be best if you sent a tank sample off to a water testing company to see what your copper levels are at. AWT is the cheapest although some of their testing equipment has been questioned. I'm not sure how accurate their copper test equipment is.

FWIW, the copper test results I have seen from AWT come back in the expected range.

Randy or Boomer may know more about the AWT copper testing method. :)

[wooden_reefer]

I have always obeyed the rule about not using calcareous material that has been treated with copper in a reef tank, but I really don't know precisely why.

If it is copper carbonate that is formed, the solubility product of copper carbonate is very low.

If the rock is not used for a while, worth trying I think is perhaps acid baths to flush out the copper. Some rock surface will dissolve and some copper may actually dissolve in acid water. Possible I think.

[HighlandReefer]

Interaction of copper with the surface of calcite
http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=5532821

From this article:

"The interaction of Cu ions in solution with the surface of calcite has been studied in a range of solutions from pure water to seawater. Observations of the uptake of Cu from solution onto calcite indicates that the process is rapid and strong in both distilled water and seawater. In distilled water, Cu uptake is directly proportional to the concentration of Cu in solution; Cu/sub s/ = K/sub s/Cu/sub 1/. The average value for K/sub s/ is 3.5 +- 1.7. The Cu/sub s/ dependence on Cu/sub 1/ is linear over the entire Cu concentration range studied (0.1 to 200 ..mu..M). Results do not indicate the formation of a precipitate of either malachite or copper carbonate. A precipitate of the form Cu/sub x/Ca/sub 1-x/CO/sub 3/ may be deposited onto the calcite surface in distilled water. The value of K/sub s/ in distilled water decreased sharply over the solid to solution ratio range of 0.1 to 2 g CaCO/sub 3/ 1/sup -1/. This was followed by a small change in K/sub s/ for solid to solution ratios in the range of 2 to 10 g CaCO/sub 3/ 1/sup -1/. In seawater, the uptake of Cu is also directly proportional to the concentration of Cu/sub 1/ up to a limiting value of approximately 13 ..mu..M. The average value for K/sub s/ in seawater, 0.24 +- 0.06 (Cu/sub 1/ less than or equal to 13 ..mu..M), is approximately an order of magnitude less than in distilled water. This is probably the result of smaller Cu/sub 1/ activity coefficients and increased site competition by other ions in seawater. Attempts to increase the Cu/sub 1/ concentration above 13 ..mu..M resulted in the additional Cu being deposited on the surface of the calcite. A possible explanation for this behavior is the formation of a precipitate of malachite on the calcite surface. The value of K/sub s/ decreased slightly with increasing solid to solution ratios in seawater.

[wooden_reefer]

"The average value for K/sub s/ in seawater, 0.24 +- 0.06 (Cu/sub 1/ less than or equal to 13 ..mu..M), is approximately an order of magnitude less than in distilled water."

Good article.

I wonder what 0.24 +- 0.06 means.

If it means that it is a range. my observation that the rate of precipitation of Cu is rather predictable is correct.

Directly proportional also means with the Cu conc is high, the copper drops faster by proportion, which is good in a more stable cu level in treatment.

[bertoni]

I suspect that +/-0.06 the .95 confidence interval for the parameter, but I'm just guessing.