it takes alittle time for ponds to settle if it is a newish one.lillies are good for covering the water surface if the pond has midday sunlight,they all have different depths of planting so check the label,but if you have any koi carp then beware.i have two and they go down the bottom and disturb the muck on the pond floor and will eat some of the plants.my pond isnt as big as yours but its a combination of the right amount of fish to the number of plants.you need to cover some of the surface from sunlight to stop the water going green so marginal plants are good i have 'myosotis'(water forget-me-not) as its a blue flower and fills out nicely,but you need oxygenators for a clear pond,'elodea crispa'(goldfish weed) is the most common one,i use it as it can be thinned easily.frogs at the moment are starting to be active and you may find they are churning up the silt at the bottom as well.good luck i hope that helps a bit.