I'm working on making a chiller, and for the sump coil I'd like to try using a material with high thermal conductivity but it needs to be reef safe/salt water proof. I really only have 4 choices of materials that have high heat conductivity that I know of, aluminum, copper, silver, and gold.
I'm pretty sure aluminum and copper are not reef safe, so I'm considering a silver or gold plated copper coil. Silver would obviously be cheaper, but if it's just going to corrode or kill fish I'd like to know. Gold I'm pretty sure would be fine but probably expensive.
As a second option I'm considering ultra-thin pvc
or silicon tubing. There is a huge difference in thermal conductivity, so it would have to be really thin to make up for it.
Whatever option I choose I want to be 100% certain the coil in my sump wont leak or poison my tank.