White slime ID

Anyone know what the white, gooey slime that coats the outside of my
flexible, 1/2" tubing might be? It only appears on the vinyl tubing, not on
the stiff tubing I use. It makes the tubing slippery to handle but doesn't
seem to harm anything. I use the flexible stuff to connect my powerhead
output to stiff tubing used as a spray bar.

How else to describe it--bits of Casper, the friendly ghost.

One plant tank with no fish, just some driftwood, Java fern, sword, and
pennywort, has bits of Casper seemingly growing out of the black gravel.
What might this be? Thanks.

Greg. Tong
San Francisco, CA, USA
gtong at sirius_com

"Every infinity is composed of only two halves."