DO NOT USE COPPER ANYWHERE (except wiring!).

[Jollyrancher]

"I suggest you talk to a fertilizer company."

I'm the research director for a very large horticultural corporation. We use copper tubing in our multi-stack NFT systems with all sorts of fertilizers. We have no issues because we got non-treated copper piping.

Try cutting open a piece of your plumbing and check it for etching.

Good for you that you don't have any issues.

Like I said, talk to a fertilizer company, I did.

My system is a hybrid DWC/aeroponic