Under good light, Slavinia minima will quickly spread to cover your entire tank, unless you manage it. Excellent for sucking nutrients out of the water, and very pretty. Easier to control than duckweed. illegal to own in some southern states
It looks like it's a highly invasive water fern in the US so be careful if you own some, I just got a single piece by accident in some Riccia I purchased, I'm going to see if it will grow and divide but I'll make sure it's dead when it goes in the trash.
I think Salvinia Minima is even more invasive then duckweed. In the tanks I keep it in it out grew the duckweek, almost wiping it out. I actually like Salvinia better than duckweed since its larger and grows in connected clumps its much easier to handle.
This plant is handy as it provides a place for my African butterfly to wait under. as people say they are very good at removing nutrients from the water, and grow well under good lighting. the only problem i have currently is that my PH in my tank will not seem to fall below 7.5 even with added ph down. however they are still growing, just slower than usual.