surface scum

Hi all,

I have a 90 gallon heavily planted, cichlid (Malawian), tank
(with too many fish, but that's another story). Anyway,
whenever I get a vigorous spurt in plant growth, I also get
a heavy dose of scum on the surface of the water. Is there a
connection here or merely coincidence?

Bill Edwards 
Survey Research Lab 
Arizona State University