Neptune's years are 164.8 Earth years. Its days are 16 hours and 6.7 minutes long. Although Neptune's days are shorter than our days, its years are still longer than ours.
Most colorants will last in your pond approximately 30 days. You may have to add more pond dye before 30 days if you have execissive rainfall, run-off, a heavy out flow, or evaporation. If your colorant is fading you will visually be able to tell and should add more dye to the water.
Check for the cause of any cloudy water. Scoop pond water up with a clean, clear glass jar. Put the jar of pond water in sunlight for 4 to 5 days. Algae will move about constantly in the water and will turn the sides of the jars green or brown. Silt will all settle at the bottom of the jar and will not move about. Treat the pond for excess silt. Throw in 100 lbs. of hay to treat silt caused by clay soils.