How much direct sunlight?

lee wrote:
Plants in the vegie filter and pond are not growing strongly. Water cress
leaves are very small despite a good root system and plants in the pond show
little growth. pH is 8.4. GH 60 mg/L KH 120 mg/L.
Pond is 1000 gallons and has 5 koi and 6 goldfish. Day time temp is 17c.
Feeding plants with potash and epsom salts has helped green up the leaves a
little. Anyone suggest how to get the plants into growth. Many thanks. C.