FlytrapCare Carnivorous Plant Forums

Yes, copper is toxic to plants. Most normal plants would probably be OK, but carnivorous plants are more sensitive. The copper ions released into the water would likely kill them before too long.

Science lesson kids, gather 'round.
Why do you feel you need to ground them? No other grower I have encountered has ever said, "You know? If only I had grounded my plants...".
Copper pipes are used to deliver water to houses, yes, but we're not plants. While excessive copper is toxic and can cause problems, even death. It is also an essential mineral used in many aspects of our cardiovascular system.
For people, the upper safe limit is considered to be 10 mg of copper consumed per day, with a recommended intake of less than 1 mg per day. Even in houses that still have copper pipes (pipes are transitioning to PEX piping), the water isn't acidic enough to draw the copper ions out in any appreciable concentration unless the water system isn't used for an extended period of time, and the water doesn't move. Then it might be a problem.
With normal soil, a healthy copper amount is less than 50 mg per dry kg, but the plant isn't taking up all of the copper as its roots aren't in contact with all of the soil.
Where carnivorous plants evolved to live in nutrient poor soils, including soils lacking in trace metals, the copper ions that will be shed into the standing water from a (in my opinion unnecessary) copper grounding cable could negatively contribute to the long term health of the plant.
Although plants in situ are naturally grounded, there is ample evidence in billions upon billions of potted plants worldwide showing that a plant performs just fine without a potentially toxic metal connecting its water source to the earth.
However, in the end, it's your plant. If you want to rely on a YouTube video (using cut flowers, but no evidence if they were all cut together, or if the one that was grounded was cut two days after the others) and a single article (albeit an article from a definitely credible source), do your thing baby!

Lotus wrote: ↑Sat Jul 10, 2021 11:09 pmthe copper rod is not touching the soil or the sphagnum, its just in the water, but maybe the water goes acidic? What if I leave a tiny bit of the copper in there, anyway, time will tell.

The media itself is acidic, and, since it's sitting in water, the water is acidic. Copper in the water, peat, or sphagnum would all likely have the same result; a slow death.
But, your plant, you do you.

Stainless steel is better, less reactive, but not necessarily safe. All metals, just by their very nature, will leach elements in an acidic environment. These plants grow in an acidic environment. In this case, you're trading copper ions (which are definitely more toxic) for iron, chromium, and nickel ions being introduced. However, nickel is a known carcinogen.
Yes, stainless steel is used in many applications surrounding food, including utensils that you put in your mouth. But that momentary contact vs weeks or months of sitting in an acidic environment do not come close for a relevant comparison.
I guess the big question is, at least in my mind, why do you feel that grounding the plants is necessary? Billions upon billions of living and thriving potted plants prove that it is absolutely unnecessary.
Don't get me wrong, they're your plants to do with what you wish, but I can find very little evidence to support this claim that grounding is beneficial. The few articles I do find are laced with ads for ready made grounding devices you can purchase, give instructions on how to make grounding devices to plug into an outlet (yikes! DANGEROUS!), give references to "experiments" conducted, but give no data about the before, during, and after, or refer to people they claim are experts on the subject, but give no links to their online information, nor citations to their published works, and none of them have any mention of this being applied to carnivorous plants. That is the main focus of your question, and there is plenty of published evidence to, 1. support that these elements are toxic to carnivorous plants, and, 2. these elements will leach out in an acidic environment.
I'm not saying it's BS, but I'm getting a feeling that this is the equivalent to the ads for "X-Ray glasses" that used to be on cereal boxes when I was a kid.
If you can conduct and document an experiment that proves the benefits of grounding your potted plant, great. You'll be ahead of the vague claims of success I could find.
Good luck.