Floating Plant Questions

So I have a few questions about floating plants. What can you do with them other than just having them floating there?? Is there a type of fish that needs them to breed or a fish thats eats them. Please fill me in on floating plants I have some and trying to have them multiply cause I just got...
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I use floating plants for guppy fry. My angels enjoy the hunt.

TR
 
Some are nice like Red Roots and Indian Fern. Little fishies (or at least mine) love swimming through the root systems.

Others can be a nuisance......a.k.a Duckweed. I'm actually going on an erradication mission this weekend to remove it. But....goldfish love it!
 
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