Here are tonight’s pics at lights on. I’ll include the pic I took when I first put the copper circles in the tote for comparison.
Im starting to wonder if maybe the roots actually like the copper!! 
I see no signs of browning and they seem perfectly hapy to grow right across any copper and down into my drain tubes!
I found two more pics showing how much damage can be done in a short time. Remember this was a 2 minute test.
The piece of aluminum is about 1/2" long x 1/4" wide x 1/16" thick. Its corroded down to a few bits and the copper wire on both leads is mostly gone as well.
Yeah, which is why I said earlier that people were probably seeing that effect and freaking out 
Well, this is a bit disappointing for what you were trying to accomplish. Whatever the outcome, an interesting and great test.
Perhaps. I thought there was at least one report in this thread where they were seeing the results of copper toxicity in the plant. Who knows what the physical concentration was in that case or, for that matter, how quickly it got to the point of toxicity. I suppose if someone was running solution through copper coils, something electrical in the system could be creating a current loop to accelerate the decomposition. Hopefully, not nearly as dramatic as your battery discharge tests. If anything, the amount of copper contact would probably be an order of magnitude greater than what we are seeing here even without the electrolysis component, I’'d think.
Personally, I’m still a bit concerned with the general copper in solution question. Some things just aren’t adding up for me at the moment. Not with what you are doing but along the lines of what the various research papers have presented along with the various nutrient formulations with widely ranging copper concentrations.
A couple of things I’m starting to grasp is that the actual uptake of copper must be significantly complicated by the ratio of other minerals in solution. Zinc, for one. Otherwise, I cannot understand how we are getting away with these high levels of copper reportedly in our nutrient formulations. Not to mention, potentially adding more into solution. You’ve got me thinking a bit too much on this. I’ll gain a better understanding eventually and would like to post any additional information I dig up in this thread. If that’s ok with you.
How long are you planning to run this test for? Before you complete your experiment, would you mind running an additional test for free copper?
More comments later, but I will for sure test for copper again - maybe today. My meter is due back today, and I may need to do a rez change depending on the readings I get.
Im going to leave the copper pieces in there until the roots start to impact water flow in the drain. That may not be much longer though!
Not sure why I didn’t get either of the mentions, but I am just seeing them now. This was published about 3 years ago:
Because of the fertilisers in a hydroponic solution, it is very corrosive to metals such as copper, which is also the major component of brass. Therefore, your pipe and fittings would gradually corrode away until useless.
However, this is not the major reason for not using them. Copper is a plant trace element (also known as a micro-nutrient). In a hydroponic solution there is a range of copper concentration, which is essential for plant growth. Lower than this and the plant develops deficiency, which leads to reduced yield and quality. Higher than this and the plant develops toxicity (also known as phyto-toxicity), which leads to reduced yield and quality, and if it goes further, eventually to plant death. Using copper/brass pipes and fittings can easily lead to the copper concentration in the hydroponic solution rising to toxic levels, especially if the solution is recirculated.
Pipes and fittings for use in hydroponic systems need to be inert to corrosion. The usual material is black polyethylene (Polythene), which is relatively cheap and doesn’t corrode. It is readily available from hydroponic or irrigation retailers. Also, ensure that any pump you buy will also not corrode. Small pumps for hobby-sized systems are often plastic. Larger pumps often also have some components made of stainless steel.
…
I only found this after having tried using copper myself, but I was using it more in a coiled spool in conjunction with a chiller to keep a rez cool, and watched it kill about 50 plants inside of a month.
Of course in this experiment the copper is far less, but does not change the fact that the nutrients break it down.
crikey
this is an example of why i recently wrote that hydroponics is often more labor-intensive… ay caramba.
<— likes dirt
On the question of copper uptake in plant material:
Averaged data as calculated from “Mineral Nutrition of Cannabis sativa L”, S. Landi 1997
Figure does not directly address excess nutrient beyond sufficiency but otherwise provides an interesting look at where the nutrients end-up.
Im in a rush, so a short report.
The copper is out of the system - for two reasons.
Last week I noticed my PH seemed to be getting wonky and not staying stable like it had been. I figured it was mostly due to using drops and not being able to read it accurately. Then I got my meter back, and sure enough, my PH was waaay low. I PH’ed it back up - several times - and it just kept dropping like a rock, So, I did a rez change with a fresh water rince, and after putting it all back to normal - the PH was still dropping like crazy. It has never done that before.
Anyway, after lots of head scratching and searching I finally realized that the copper was the only thing I had changed/added to the system. The roots were ignoring the copper, so I took it out.
Within two hours the PH stopped dropping and its been almost perfectly stable now for 12 hours - back to normal.
Im gong to monitor the roots with the copper out to see how long it takes them to grow back. Its possible the copper slowed them down some, so I will compare over the same time frame.
Some quick pics.
Just for you for a second data point - I just mixed up a small batch of Mega Crop at PH 6.24 and EC of 2.95mS. I put those same copper pieces in the mix. I’ll keep and eye on it for PH changes and test for copper every few days.
By the way, none of my copper pieces turned green - just brownish.
Im curious what symptoms the plants showed - where they specific to copper or?
Did you notice any PH issues?
Also - what did your copper coils look like when you pulled them out - green or brown or like freshly sanded, kind of orange colored copper?
Im asking to help determine if your problem was at least partly due to electrolysis. The out gassing you mentioned before was a big clue, but Im wondering if there were others?
I found this reference to what is actually in the copper ‘patina’ that develops when copper oxidizes. You wont get this patina if there is electrolysis going on. There may be other chemicals produced when it is exposed to our nutes so I dont think this is the end all list of possible toxins.
Unlike other destructive oxidation processes, the patina acts as a protective layer, and it does not cause any weakness in the metal. Thus, copper is considered as an important element that is resistant to corrosion. The patina prevents further corrosion of copper beneath the oxidized layer. Very often, this layer is seen on the rooftops of old buildings, and acts as a waterproofing and sun-proofing coat.
☞ The oxidation process is characterized by the formation of three main products: azurite, malachite, and brochantite. These minerals impart the characteristic bluish-green color to oxidized copper metal and form the patina layer. Simply speaking, it is a redox reaction wherein both oxidation and reduction take place at the same time.
☞ Firstly, copper donates electrons while reacting with oxygen to form copper oxide, which is reddish brown in color. This can be represented as:
4Cu + O2 = 2Cu2O (copper oxide) ---- equation 1
☞ Cu2O again reacts with oxygen to form CuO, which is black in color:
2Cu2O + O2 = 4CuO ---- equation 2
☞ The atmosphere also consists of various pollutants like sulfur dioxide, carbon monoxide, carbon dioxide, etc. In areas where combustion of coal takes place, sulfur fumes are present on a large scale, as sulfur is an impurity present in most of the coal types. Copper oxide reacts with this element to form blue-colored copper sulfate (CuS), which may further react with carbon dioxide and moisture present in air to form the patina layer.
Alternatively, the copper oxide may also directly react with CO2, H2O, and sulfur oxides to form the compounds brochantite, malachite, and azurite:
☞ Brochantite is mainly formed when high level of sulfur fumes are present. It is green in color, and is also known as hydrated copper sulfate.
4CuO + SO3 + 3H2O = Cu4SO4(OH)6 (brochantite) ---- equation 3
Interesting data, but like almost everything we have come up with so far - it raises as many questions as it answers 
I think the only way to get more info would be side by side runs with and without copper followed by tissues sample tests.
Ok, there are still a lot of unanswered questions, but here is my take on using copper in hydro systems.
There is no up-side that I can see as far as root control, so why risk it?
I have to admit I am both surprised, and disappointed in my results. I was sure the copper would at least slow down the roots, but I especially didnt expect the PH issue.
By the way, Im not at all sure whats going on with that PH thing. Its clear the copper was, in some way, contributing to the rapid PH drop because it stopped after I removed the copper, however two things make me wonder about that.
The PH is starting to drop again, but at a much slower pace. When the copper was in, the PH would go from just over 6 to near 5 in 8 to 12 hours. Now its maybe a .16 drop (or less) in 12 hours, so at least a ten fold improvement - but it is dropping. That makes me wonder if the copper has damaged the roots in some way that doesnt show or is causing something else to happen? Its also possible my nute balance is off. Ive been chasing the PH so much the last few days, Im considering another rez change.
The water sample I set aside for @Viva_Mexico is NOT dropping in PH - its going up slightly - but it has no roots in it.
In any case, its clear the answer to the question “Can copper be safely used in hydroponics to keep roots out of drains?” is a big fat NO. I think we can shorten that to "Can copper be safely used anywhere in hydroponics systems? = NO!
Yes, that was in response to 99percents question as to where the minerals end-up and partially answers whether having additional Cu in solution would result in increased Cu in the leaves and flowers. Still do not have a good handle on the relative Cu in solution as a ratio to other mineral nutrients but I think some further studying of the available literature might shed some insight. Of course, the literature specifically for canna remains a bit limited so we end up having to extrapolate today.
Yup. You’ve given us some insight into potential questions beyond the first order question for which, it appears, would require an additional level of rigor in order to produce provable results. As you’ve noted, it seems tissue samples would be needed to figure out the why and whens since there seems to be a gap between the research and the on-the-ground experience. Would be nice to budget for such experiments at some point. But, this could be a relatively expensive proposition whose payout may only bring more questions.
Thank you for sharing your testing. It was insightful.
I don’t think he actually meant out-gassing (as opposed to dissolved/contribute into solution) though. Perhaps @LED_Seedz could clarify.
I thought I used the term off gassing, but if I didn’t my apologies but that is what I meant. A chemical breakdown in direct relation to the copper it’s self and a bi product being added in to the system that I can not either verify nor test for because I simply don’t have the equipment nor reason to think the risk was ever worth the reward.
The first sign of the plant dying back was a tinge on the outside of the leaves, but looking over watered at the same time with dropping leaves and more than normal die back. When I pulled the plants out most had rotted root systems that were mush and I have used chillers forever.
I have also run perpetual for years and plants in every stage were being effected.
When the copper coil was pulled out it was black, and it had a smell coming off of it not like the nutrients. This was also at least 5 to 7 years ago so a lot of the details I recorded are gone unless the site Cannetics logs are around.
Not sure what other questions there may be at this point. Using copper materials and hydro do not go together and that’s really all we need to know at the end of the day.
I found excess copper blocked iron absorption so all mine went bright yellow. I was running my nutes through copper piping though so I may have had just a little more copper in my water than if I had used a coil, or some copper wire.
Ok, I took the gassing part of out/off gassing literally. When there is any type of current flowing in the system - from electrolysis or galvanic corrosion - you will have actual bubbles of gas being given off at each electrode. Thus off or out gassing. Meaning literally some gas coming off of or out of the solution.
The copper being black could still mean you had some electrolysis going on. If the copper was on the positive end of things it would just look eroded and like orangish color copper. If it was on the negative end of the system it will take on the color of the metal on the positive or opposite electrical electrode - as in electroplating.
You’re right though - bottom line is the details really dont matter. Copper is bad stuff in hydro
