White plaque on tubing

Hi folks,

In various places in my tank and sump, I have noted the accumulation
of a very slippery white film on pieces of vinyl tubing. The film
appears everywhere the tubing is in contact with water, without regard
to light.

As I have seen this on at least three different kinds of tubing, *and*
on the power cords for my submersible heaters, I'm assuming it's not
some chemical leaching thing. My current operating assumption is that
it's some (probably harmless) bacterial plaque. It comes off
trivially by rubbing.

Anyone know what this is, and whether it's something about which to be
concerned?

--Trapper