Duckweed?

[goldfish_is_orange]

Go for salvinia or frogbit instead. Duckweed is ridiculous stuff. Once you've got it, theres no going back!

+1 on the frogbit!

 

[Retired Viking]

I use salvinia in my tanks, I could walk about 2 hundred yards and get all the free duckweed I want out of the near by river but IMHO salvinia is better

 

[vanalisa]

I have a tiny bit. It's there, next to my latest attempt to grow frogbit. I happen to like it.
Go ahead, laugh.

 

[TheTenthDoctor]

It depends. Some people love duckweed. I have mixed feelings on it. You don't really know until you keep it