I have the type goldfish and koi eat ...

What kind (of duckweed) is that?
C//

Well.... there's true duckweed that is a small shiny smooth leafed floating
plant that goldfish and Koi love. Then there is Azolla or Fairy Moss that
some people call duckweed by mistake. Similar shape, but dark green (and
can also be bright red) and fuzzy. ~ jan

~Power to the Porg, Flow On!~