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re how much cu is toxic?

Repeating what others have already replied: the answer depends on the water conditions and the species in question. Hardness and chelating organics in the water will reduce toxicity. 

>From experience I can say that plants which tolerate a high copper content include most Echinodorus, Crypts, Anubias, Hygrophila, Microsorium and Lotus. Mosses and of course red algae are sensitive. Tetras are included with species of fish which tolerate high Cu levels. Otos do not like high Cu levels. Corys and livebearers are said to be very sensitive. 

Snails, shrimps and other invertebrates are especially sensitive.

I use copper occasionally to kill any red algae that appear in my tanks, with a syringe of concentrated copper sulphate solution dosed directly on the algae. I do not have sensitive organisms in my tank except snails and moss. I know when the level of copper has become toxic when the snails retreat into their shells and start producing mucus strings. When this is noted and copper dosing is stopped and the moss is not be effected.

I would therefore suggest that snails be used as indicator organisms for copper toxicity. If freshwater snails (eg ramshorn) do not act strangely when put into the test water (ie staying withdrawn, releasing large amounts of mucus) then the water is safe!



Date: Wed, 23 Oct 2002 10:15:07 +0200
From: "Davorin Palijan" <davorin.palijan at os_tel.hr>
Subject: How much Cu is toxic?

I wanted to ask for safe levels of Cu in planted tank.
How much Cu can fish/plants/snails tolerate without
ill effects?



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