Strange plant in container water garden

I've never had this happen in the five or six years I've been planting a container water garden. I hope somebody can help me identify this totally rampant grower in my water garden. I took out a lot of it a couple of weeks ago, but it just multiplied like Topsy. I had a water lily planted in the container, but this stuff has obscured anything but itself. When I first planted the garden I put a handful of duckweed in it which was doing fine until it got run over by this stuff. Any ideas about what it is and what I can do about it?

Here's a close up of it in July.

Another another. It also has a clover-like growth in the garden. I had cleaned out most of the rampant grower in this photo. I don't know how these got in here, unless it came from the place I bought the plants from.

This message was edited Aug 5, 2008 11:13 PM

Rev, are you worried about the dark green one or the light green one?

I have whatever the dark green one is in my pond this year, although I know where it came from. I brought a tiny piece of it back from the lake my parents live on in Houston. It has multiplied like great guns, I should've known better. I am assuming the winter will take care of it, but I dont know what it is.

The light one is duckweed, no problems there. The clover-leaf and the other dark green one are the ones I'm worried about. You have it in your pond? How big is your pond?? It's got to be some kind of algae or something.

The plant is an Azolla. Probably Azolla caroliniana - Mosquito fern or sometimes called water fern. Some pond plant stores actually sell a Duckweed Azolla mix, I suspect because you can't ever separate the two when they are growing together. What can you do about it? Not a thing. Azollas are hardy to zone 5. So, don't let it escape anywhere where it could threaten other native water plants. Fish do eat it.

Azolla isn't what I have. This one is a lot larger than the 'leaves' of Azolla. Not large in the grand scheme of things, but they some of the leaves are almost the size of a dime. I'll go try to get some pics.

Oh I see the azolla in her picture, I didn't see it before Snap. Good eyes. I have received Azolla attached to plants from local pond stores, but never really had a problem with it taking over.
The other one in the pic is what I have (I think it's the same). Here's a pic of what I have. My pond is about 900ish gal. Do you think it's the same Rev?

And apparently my memory didn't serve me very well, because it's not the size of a dime, a bit smaller.

I think I figured it out. Salvinia natans. Looks like it's not hardy here, so that makes me feel better.

http://www.botanik.uni-karlsruhe.de/garten/fotos-hassler/Salvinia%20natans%20BotKA%20S2.jpg

http://en.wikipedia.org/wiki/Salvinia

They all have their place in a pond, water garden or tub garden - if - the hardy ones don't escape. I wish I could have some but the skimmer in my pond cleans it right out in an hour. I particularly like the Salvinia natans. About the Azolla, if you let the surface of the pot get dry and fry in the sun you might get rid of it. Any way you could do that without sacrificing the lily?

Art, I think that's it, but mine looks a little more like a three leafed clover. But the surface looks the same. The other plant looks like Spanish Lace, but It's gone rampant this summer and smothered my lily. I can't keep up with it. I'm not going to buy from that vendor again, it must have come in with the duckweed, though I didn't notice it.