If I may be the voice of ignorance in this thread. Zinc and Copper become toxic if present in large amounts, but are also trace elements needed by living organisms. In fresh water aquariums we used copper-based medication straight into the water to deal with a great many illnesses related to parasite infections. Invertebrates does not like copper in high volumes and your worms may be the first to be affected by it. Looking at the size of the copper element and the volume of the fish tank, I'm nit sure how much will have to leak though. Same philosophy on the zinc. I'll do a search on zinc and copper toxicity if I have a gap today as it may be a recurring question. People get very sterile when they do AP, but if you look at nature - rock and soil, you will find these elements. It all boils down to the amount that is going to escape into your set-up.
Freaking out if your house is like mine and water is delivered through..........you guessed it: Copper pipe. Is my rain water safe if it was captured on a zinc-plated roof?
As an aside... it has been shown in many studies that Calcium hardness significantly affects survival of juvenile
fish exposed to a toxic concentration of copper sulfate in low alkalinity water.
But, magnesium hardness provided no protection from copper toxicity.
Note... the studies refer to low alkalinity water... low pH...
Calcium Hardness is a measure of carbonate buffering in the system....
Magnesium hardness is a measure of the mineral content of the water, usually Calcium * Magnesium... and known as general hardness, often referred to as "hard water"
Sorry Kobus... but I'm going to have to agree to disagree.... the studies relating to copper toxicity... are long and varied... and consistant...
Bare in mind that AP systems are recirculating by nature.... and almost all metals are cumulative in fish protein...
Put copper & zinc in your systems if you want... I wont!!!
Let me re-focus my replies in this debate. I know the studies concerned with copper and zinc paint a bleak picture of the two elements. Also that they are most dangerous in acidic, unbuffered environments. That said, many parts of the world, including my house, have copper pipes and galvinized iron roof sheets. I am willing to have tissue samples of any dead fish sent of for analysis, as it is of interest to me too - Just none of them had died yet. For me, at my setting, these two elements are difficult to avoid. Animals and plants require copper and zinc to grow. Below is an abstract of a paper on copper requirements of plants:
The copper (Cu) requirement of four crop species was measured in a glasshouse experiment using yield of dried shoots and Cu content (Cu concentration multiplied by yield of dried shoots) of 62 day old plants grown in two different alkaline soils. The species compared were faba bean (Vicia faba L. cv. Fiord), chickpea (Cicer arietinum L. cv. Tyson), lentil (Lens culinaris Medik cv. Digger), and spring wheat (Triticum aestivum L. cv. Stretton). The comparative Cu requirement of the species was determined from yields of dried shoots when no Cu fertilizer was applied, the amount of applied Cu required to produce the same percentage of the maximum (relative) yield of dried shoots, and the Cu content of dried shoots. The concentration of Cu in youngest tissue and in dried shoots was used to determine critical concentrations of Cu in tissue associated with 90% of the maximum yield. Faba bean used indigenous soil Cu more effectively than wheat, followed by chickpea and then lentil. As measured using both shoot yield and Cu content in shoots, the Cu requirement was lowest for faba bean, and increased in the order faba bean < wheat < chickpea < lentil. Copper concentration in dried youngest tissue and in dried shoots increased with an increase in the amount of added Cu. The critical Cu concentration in the youngest tissue was (mg Cu/kg): 4.6 for lentil, 2.6 for chickpea, 1.5 for wheat, and 2.8 for faba bean; corresponding values for dried shoots (mg Cu/kg) were 6.3 for lentil, 3.3 for chickpea, 2.8 for wheat, and 3.0 for faba bean.
Keywords: Copper requirement; Pulses; Spring wheat; Critical Cu concentration
I have also attached a short paper on zinc requirements of plants. What an interesting debate this can spark: Does the copper and zinc needs for a planted AP system exceed the levels that can leach from a house with a steel roof and copper pipes? I have not been able to get hold of exact data on fish, human zinc and copper needs, apart from picking up that these elements cannot be synthesized and therefore has to come out of our diet.
This is the basis for my lack of hysteria on the topic. Everything needs these elements in moderation. Let us establish what is moderation and what is risk, in stead of just going ballistic at the mentioning of their names.