silver grey web with black dots in bottom of pond

[peom]

Hi all,

thanks for help with my other stuff, the green thing turned out to be a snail, of which we now have 2 definately and possibly another small one and the water cleared by itself.

But now it has cleared I can see a web type thing it is silver grey and almost looks like a massive spider web covering the bottom of the pond which has black/brown dots in it (larva of some sort?) could it be a weed or something and if so do i need to remove it?

Thanks all help appreciated. Also something has eaten a lobelia plant right down to the ground any ideas on that.

Thanks again
Pauline