duckweed dome

so go read this about duckweed
http://www.kval.com/news/local/117947779.html
they show how you can grow duckweed and use it to heat your house for the same or less than coal heat !
here is the place that was selling systems,
http://www.pacificdomes.com/

but domes are easy to build on your own and are cheep, learn how here
http://www.byexample.net/projects/current/dome_construction/
or here
http://domehouses.blogspot.com/2011/07/building-20ft-geodesic-dome-shelter.html 
or here
http://www.weasel.com/dome.html

just install it over your pond and cover with clear plastic

you can also grow fish in the pond,
the fish will fertilize the duckweed as well,
and you can eat the duckweed as well,

the big trick to growing duckweed is to make sure it has total coverage of the water.
and just let it grow thicker

just think of the possibilities,