Copper and fish

[M Cosmo]

I want to add a heater to my fish tank and it has a small temp sensor. Here is a pic.

It is about 4 inches long. Will this small amount of copper poison my fish. I have about 600 gallons or more of water in the system.

Ron is using the same heater and he encapsulated his in a bottle and sealed it.

I was thinking of just painting mine with some clear since it won't be hotter than 80 in the tank.

[TCLynx]

Get them into copper free water and they may recover, it's hard to know for sure, depends on how much damage they have already endured.

The acidic corrosive nature of aquaponic water will leach copper and zinc more quickly and make them more toxic to fish than in a very high pH environment.  I've heard of people keeping some fish for a long time in a galvanized stock tank before any ill effects were observed but in any environment where the plants will be happy, copper or zinc are likely to cause harm to fish eventually.

[Pierre Riche]

Right, the PH is about 7.4 so acidic doesn't seem to be a problem. I think i'l move them into copper free water and maybe they'l make a comeback. 

TCLynx said:

Get them into copper free water and they may recover, it's hard to know for sure, depends on how much damage they have already endured.

The acidic corrosive nature of aquaponic water will leach copper and zinc more quickly and make them more toxic to fish than in a very high pH environment.  I've heard of people keeping some fish for a long time in a galvanized stock tank before any ill effects were observed but in any environment where the plants will be happy, copper or zinc are likely to cause harm to fish eventually.

[David R. Russell]

If you are a hydroponic crop producer and make your own fertilizers- you are likely familiar with both copper and zinc sulfate as both are widely used.  Both Cu and Zn are trace elements needed by plants.  The question is whether or not the leaching from metal will cause levels to become toxic rather than beneficial. Depends on size of system, amount of metal in system and quantity of plants. For lettuce recommed copper level is 0.1 to 1 ppm and Zn 0.5 to 2.5.  Copper sulfate is legal in some aquaculture applications.  Typical levels for circumstances with fish present is 0.3 to 0.5 ppm for several days.  Copper usually has to be added each day as bacteria and other microorganisms seem to have an appetite for copper and will sequester it. 

[RupertofOZ]

There's no disputing the fact that Cu & Zn are essential trace elements for both plant and fish growth... but they're both trace elements... and only needed in miniscule amounts...

You'll get all the Cu & Zn both your plants and fish need... from any quality commercial fish pellet feed...

 

The recirculating nature of AP... and tendancy toward metal accumulation in the flesh of fish... means that any metal leaching... will become toxic eventually...

 

Yes, copper sulphate was used in aquaculture.. for disease control... basically it killed any nasties dead... but it's basically been banned, or rapidly phased out in nearly all countries...

Copper Sulphate is, or at least was... also the primary ingredient in marine anti-fouling paints... now also banned... because, as a result of using it... the entire populations of fish, crustacea, corals etc... in marinas... were wiped out...

 

That alone should dispel any doubts as to the toxicity of copper to marine life...

[David R. Russell]

Copper toxicity is a complex issue and many different environmental conditions influence it.  In small freshwater systems that are more acidic, have low alkalinity, low calcium, and a portion of the system that has anaerobic conditions as one might have in some aquaponic designs- copper has a greater likelyhood of causing tragedy.  Better to be safe than sorry and limit/avoid use of copper metal in such systems.  Copper will become toxic for fish in an aquaponic system long before it will be an issue for the plants and people consuming the plants.  In marine environments, for most of the above being opposite (lots of calcium, high alkalinity, high ph), make copper much less toxic. The red antifouling paint, copper I oxide, is the anti-biofouling compound that has some negative environmental impacts and is being phased out and banned in some counties.  Industry is now experimenting with cages made of copper metal instead, which does not have the problems with the red paint flaking off and causing benthic problems.  Copper sulfate, which is copper II (the blue stuff) is still widely used in agriculture (actually OMRI approved for some applications in organic farming).  It is also widely used in marine aquaculture applications globally in situations where the operation is land based.  Toxicity is a matter of form and concentration.  At lower levels it is an essential element for good health and at higher levels it can be toxic.

 

Aquaponic systems where some copper metal may be less problematic are those with higher alkalinity, calcium is high, and ph high, and those with no anaerobic reactor for mineralizatin of fish wastes. Anaerobic conditions can transform bound copper into a toxic form.  You would also want to avoid the use of thiosulfate in systems with copper.  Such a system in aquaponics would be rare as the fish wastes would not be utilized to its fullest extent and foliar feeding would be required for the plants.  In seawater systems with very large aerobic filters which tend to scrub the water of trace metals and that also have conditions which make the copper unavailable biologically, it is possible to develop copper deficiency in the plants being grown and copper will need to be added as wastes from fish feed may not supply enough.

[jim mckee]

Howdy.

I'd re-route the copper thermocouple to the outside surface  of the tank.  Set it against the surface and glue it on.  I'd run it with another thermometer in the water to see if there is a temp difference between the two and adjust accordingly.

Don't kink the thermocouple feed wire.

jim