Neptune Tubing?

[Aspect]

Hello, I am using the Neptune DOS for daily 6 gallon water changes on my 400 gallon. I have been doing so for 6 months now and I have noticed the Neptune tubing that came with the DOS is yellowing noticeably. Is this tubing reef safe?

 

[blaxsun]

I've been using the Neptune tubing for over a year and it's yet to yellow - but it's also inside the cabinet and not exposed to any light. Yes, 100% reef safe.