Try Tetra Blackwater Extract - it's designed for tropical fish, but
       works a treat on aquatic Utrics and Aldrovanda.  It's basically
       concentrated peat extract with plant hormones and vitamins.  I
       can't comment on the effect it has on leaf colour, as I've only
       used it on my aquatics.  It also deters (though won't eradicate,)
       algae.
           Happy growing,
                       Peter
snail:Peter Cole,17 Wimmerfield Cres. :: mailto:carnivor@bunyip.demon.co.uk
      Killay, SWANSEA SA27BU,WALES,UK :: http://www.angel.co.uk/flytrap/
  vox:+44 1792 205214                 :: Carnivorous plants and seeds for sale