I got a sample of some "grey snot" algae finally and took a look under the scope:

And the species is?

Good old Didymosphenia geminata (Lyngbye) M. Schmidt
A nasty diatom filamentous grey to white snotty thing.

issg Database: Ecology of Didymosphenia geminata

This looks like the bugger.

I think Cavan Allen had the first pesky run in with this species and had a heck of time trying to beat it, thinkng it might be bacteria or BGA.

Turns out it's a diatom from hell.

Anyways, now we know what it is and that it's pretty nasty.

Regards,
Tom Barr