air bleed valve suggestions for DIY Ca reactor?

[beaker020]

I built a calcium reactor similar to this: http://jjgeisler.com/reeftank/diy_calcium_reactor.htm It works great but I am having trouble with the air bleed valves. I tried a saddle valve but they are made of brass, which contains copper, and it turned green. Then I tried a hot water radiator bleed valve but they leak. Short of ordering from aquatic eco systems, does anyone have any other ideas?

Thanks
Lance