Posted: 14/05/2013 at 14:36
Callitriche verna is a good choice for your plant. It's an oxygenating plant which forms mats of foliage. They usually blossom in March and dies during winter.
Water Violet or Hottonia palustris is also a good choice for flowering plants. They usually bloom from May to June with a bright green feathery foliage.
Water Crowfoot or Ranunculus aquatilis is also a great choice if you like flowers. This blooms white flowers during April to July. - Jane