Our ponds must be related. The last few years I get plenty of surface scum after a heavy bloom.

It starts with a heavy bloom, then turns to this...

[Linked Image]

Then this...

[Linked Image]

Then...

[Linked Image from forums.pondboss.com]

THEN...

[Linked Image from forums.pondboss.com]

I'm not trying to scare you, just prepare you should your pond follow suit. And, possibly comfort you by saying that I have not had any fish kills due to these unsightly occurrences. The only thing that changes the above course of events is a thorough flush of the pond by heavy rain events. I have done nothing but worry about them in the past.

Here is a thread that I started that has plenty of water chemistry info, links, and pond scum discussions....

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=508352&page=1

Look at the Pond Scum Field Guide link in the very first post. I believe the above photos shows a combination of algae blooms, Diatom Blooms, Protozoan Scums, and (maybe) Bacterial Scums.

Fish on!,
Noel