Duckweed

Ping and Pong, my fantail goldfish, live in a large tub in the sun porch.  The tub's amenities include a gravel floor and a little bamboo fountain that oxygenates the water and provides background music around the clock.  There are also a couple of aquatic plants, but they look meager and sparse and I thought that Ping and Pong, sociable though they are, would like a place to hide when they want privacy.

I spent some time trolling aquarium sites and found rave reviews of something called duckweed.
This plant, beloved of goldfish for its high protein content, not only gives them shade and privacy but keeps the water clean by discouraging algae and consuming excess nitrogen. You can buy half a cup's worth for $5.99, plus shipping.

I had a package of duckweed in my virtual basket--nothing is too good for P&P--when something made me want to find a picture of this fabulous plant. While Google Images was loading I looked out at the frog pond in the patio and made a mental note that it was time to yet again scoop out the weird, alga-like green stuff that has covered the water surface all summer long.  Google finished loading, and there, floating greenly on garden ponds and choking out entire lakes in South America was...the very stuff that I had been so dutifully scooping up and throwing out since the spring.

The common duckweed, Lemna minor, is a simple plant, consisting of two or three tiny bright-green leaves that lie flat on the surface of the water and trail a long, hair-like root below.  It has more protein than soybeans, which is why ducks and other waterfowl are so fond of it. It shelters the vulnerable young of aquatic creatures and takes up excess nutrients, which explains why the usually murky water of my pond has been exceptionally clear this season, and teeming with tadpoles, frogs and salamanders.  It is excellent food for laying hens, and is eaten by people in some parts of Southeast Asia.

I ran outside, scooped up a bunch of duckweed and brought it back to the goldfish tub.  Ping and Pong immediately disappeared under it.  Then I scooped up some more and called the hens.  They looked at it skeptically and backed off.  The mother superior, a Barred Rock with a bright red comb, took one bite, thought about it, took another, and the rest of the girls followed suit.  As they pecked I wondered how those people in Southeast Asia prepare their duckweed.  They probably saute it with a little garlic, and sprinkle it with soy sauce...

Lesson for the day:  before you go hunting for treasure on the internet, look in your own backyard.