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Copper(Cu)
You have been directed to this page because you have calculated a dose higher than recommended levels for copper in tanks with sensitive inverts (specifically Caridina sp. -- fancy freshwater/brackish shrimp)
Copper (Cu) is a micronutrient and heavy metal required for healthy plant growth, but is also highly toxic to inverts and fish, both in freshwater and saltwater. It is also effective in killing many parasites and is common in medications. 1 Cu is unique in that once it is introduced to a system (aquarium), it will be measurable and constant until either the plants (and trimming) or removal of material (substrate, etc) reduces levels. Too high levels of copper will result in death, while high (but not lethal) concentrations any lead to sensory loss or, at the least, behavioral changes. 1
Pesticides and medications use scientific study to determine lethal concentrations (LC) for Copper by animal species. They then recommend safe levels as half that lethal concentration (LC50). Here is a chart for common species 1,2:
| Common Name (not inclusive) | Scientific Name | LC50 (safe) ppm levels for Cu |
|---|---|---|
| Crystal Red Shrimp, Amano shrimp | Caridina sp. | 0.072 |
| Red Cherry Shrimp | Neocaridina denticulata | 0.370 |
| Rosy Barb | Barbus conchonius | 0.163 |
| Two-Spot/Odessa Barb | Barbus ticto | 0.700 |
| Giant Danio | Danio malabaricus | 0.500 |
| Flagfish | Jordanella floridae | 1.430 |
| Jewel/Eastern Rainbowfish | Melanotaenia splendida splendi | 0.231 |
| Checkered Rainbowfish | Melanotaenia splendida inornata | 0.368 |
| Stone loach | Noemacheilus barbatulus | 0.250 |
| Guppy | Poecilia reticulata | 7.187 |
| Shortfin Molly | Poecilia mexicana | 1.941 |
| Whitecloud Mountain Minnow | Tanichthys albonubes | 0.436 |
However, like all heavy metals these thresholds can be raised -- reducing toxicity -- at higher pH (and by extension carbonate hardness), but we do not recommend you change pH and KH so that you can dose more copper. Inbreeding and unhealthy fish can also reduce these thresholds -- increasing the possibility of toxicity. 4
Additionally none of these studies take into account the many other variables that could be present in our aquariums, and while the species above are common to our aquariums, to date there has not been a definitive study on ornamental shrimp in the aquarium and their thresholds for Cu. Some folks, notably Tom Barr, feel we should not model Cu toxicity at all until this data is collected. 5
However, this alert and page is meant to guide you, aquarist, using the collective studies of scientists and experts in their field. This is all simply a guide and you should exercise your best judgement.
Consider using another comprehensive micronutrient source with a smaller proportion of Copper, or, consider making your own micronutrient mix by sourcing all essential nutrients for plants.
The Effect of Copper Toxicity on Blue-Green Algae
PAN Pesticides Database (Crustaceans)