Ideas to buck up my tired pond please

There is some blanket weed alas, @strongylodon, and have also suffered from green scum on the surface in the past. What has helped on that front is having plants with leaves that float on the surface, like the frogbit and the waterlilies - as they grow they shade the surface and the algae and blanket weed don't like it.

 

As far as surface cover goes, I have a Water Chestnut which has grown a lot of roots but little leaf growth and Water Soldier which has remained mainly submerged, the dwarf Water Lily has such small leaves as to not give much cover.