Vinyl hose question

[Snappy]

I have been using the clear 5/8 "vinyl" tubing attached to my submersable pump when I transfer water from my resivoir to my mixing barrel but it always seems to give me what looks like an "oil slick" on top of the water. I can't imagine this is a good thing. That makes me wonder, what are other people using for hoses during their water change process? Please share your experiences.