Several things may help. Good plant cover on the surface, which it looks like you have. Some way to shade the pond and limit the amount of direct sunlight the pond receives to 8-9 hours per day. Good filtration and the possible use of a UV sterilizer in the filtration system. Could also have some sort of bog, plant basin filtration to aid in removing nitrates. In the past I have had a UV with a bog filter and it did help in clarity. FWIW the depth or lack of depth brings up concerns for the water temp, not much you can do about that now. Sprays or fountains could help but would really add to evaporation loss. Good luck.