Can you identify this Weed?

[Castaway]

Driving past the local duck pond, my wife and I noticed a thick and I mean thick layer of this green weed growing and covering every square inch of the pond. Now I'm not sure what it is exactly. I've seen the tiny oval shaped Duckweed growing about 50 feet away from it in the same pond but this thing looks different. Its larger and more leaf shaped and much thicker in texture. I thought GaryD could identify this. I have a bucket of the stuff but I am concerned that it may not be suitable to feed to the fish. There is quite a smell from the anaerobic nutrients that it clings to and whatever other nasties that came with it.
Any ideas?

[GaryD]

Hi Castaway,

Sorry......I can't identify it....but I can rule out some of the aquatic weeds including salvinia, duckweed, azolla and water lettuce.

Gary

[Castaway]

Thanks Gary. No problem. It'll make good compost. :)

[KenR60]

Looks very much like azolla. I also found some of this in a local Creek where it covered every square inch, added it to my 8,000 litre pond and find its growing the same, trying to cover all the surface so I find I'm scooping Buckets of it out and letting it dry out on the ground. Goldfish and natives don't eat it so I doubt if any other fish would.

[Castaway]

Thanks Ken, I found this stuff to be much more invasive than Duckweed and spreads out like a thick carpet. If you scoop it up, it reforms and fills any spare spot with its mass. It might be a variation of azolla (http://en.wikipedia.org/wiki/Mosquito_fern) as you say.

[Dufflight]

Or just azolla.

[GaryD]

I've just googled Azolla (images) and it appears that there are lots of different types. It's clearly different to the azolla that I've got. My plants are about 3mm x 5mm and are single plants rather than the fleshy type that you've got there.

[Dufflight]

The shape of Azolla is effected by the density in its growing space. Azolla forms a thick mat on the surface, this effects how the plant grows.

[Murray]

Yes, I have taken a good look at the Azolla I have growing here and my vote is for Azolla.....although I would not stake my life on it.