_Lemna minor_ is a synonym of _Lemna disperma_ (or vice versa) commonly called
"Duckweed".  There are a couple of other plants which are very similar (and
also called Duckweeds) - _Spirodela oligorrhiza_ and _Wolffia australiana_.
>Aside daphnia and aldrovanda also snails (sorry not identified yet .-( )
>are thriving well. Any idea if they can be dangerous for my aldrovanda ?
Depends on the type of snail - some can be very destructive to plants...  
Check out the snail section of the Fish/Aquaria FAQ files - they describe
various types and their effects.
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|    John Taylor  [Catweasel]    |   Royal Melbourne Institute of Technology  |
|  rphjt@minyos.xx.rmit.edu.au   |        Melbourne, Victoria, AUSTRALIA      |
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