Waterfall flexible rubber tube leaking

Question
The flexible rubber tube that carries water from the bottom of my waterfall to the top has developed tiny little holes. About the size of a pen point. What could be causing this?  I found it after I had turned the waterfall off for 5 days while I was gone.  When I returned I turned it back on and realized that it had a definite leak.  Found the leak in the tubing in several places.  Can anyone shed light on this?

Answer
Hello Daniel!
It is hard to say, but it could just be exposure to uv rays from the sun. It could also be a defect in the hose.
How long has it been on the waterfall?
It is best to bury the hoses to protect them from sunlight, or they will deteriorate.