I know for sure copper will react with the mineral salts and create a toxic soup. Stainless is OK.

small amounts of copper and brass dont pose any real problems as long as theres a good amount of nutrient volume. A few brass fittings in the setup wont hurt. Using a copper bath as a nute reservoir wouldnt be a good plan. I use brass here and there without issues

This post was edited by hex2006 on Thu, May 15, 14 at 10:48

brass fittings

Ok so after reading these I looked it up as just saltwater in copper and found that it will react to form copper chloride film, which can stunt growth, and if too much is available can become toxic levels of copper to the plants. Brass is shown to be safe by 90% of the articles I read (about 10 so 9/10). Bronze on the other hand is a big no-no... As you can probably tell from my other thread, I am working on a sustainability project, and part of my goal is longer life than that offered by plastics in sunlight. Cost will be impacted, but IF I can get a significantly longer life, it would be well worth it

Copper will tarnish (the equivalent of iron rusting). The process is slower than rusting but will increase ppm concentrations significantly when it reacts with nutrients especially with the sulfates and if you use synthetic nutrients. Your plants will continue to develop and fruit will mature but because it decreases EC, you will have watery fruit that arent as sweet as they are supposed to. If the concentration is very high, the leaves will darken to a purple hue, starting at the base and moving up gradually.