brass/copper question

[gopens]

well last week, i noticed that i had TONS of water flow in my tank from my return pump from my sump/refug. i was talking to my uncle, who is a plumber. he told me to put a valve on the return line to control flow. he said he would be over in a few minutes to help me out. he came over and installed a brass valve. it looked copper to me. so i told him that i can't have copper pipes/fittings in my tank. he informed me that it was 100% brass. and the ball vale on the inside was stainless steel and nylon. he has helped plumb many huge fish stores in the LA area. so i went with what he said. i spoke with a few local reefers and they all said it was fine as long as there was no copper. but i just wanted to hear from ya'll about this. thanks