Using a Secchi Disc to measure water clarity can provide useful information for keeping your pond healthy. A Secchi Disc is made of metal or plastic with contrasting colors that can be observed as it is lowered into the water with a string. A seldom used coffee or tea cup will work in a pinch. When the disc becomes difficult to see the depth is recorded and used to chart the water clarity/turbidity. This value will help with treatment program adjustments.
Observations: Possible Problems:
Less than 8 inches of visibility Danger of a fish die-off due to low oxygen levels and increased carbon dioxide values
8-12 inches of visibility Excess planktonic algae. Lower oxygen levels may occur after sunset until past sunrise
12-18 inches of visibility Preferred water clarity condition
18- +24 inches of visibility Planktonic algae is scarce, possible food chain interuption, aquatic weed growth increases
If you measure less than 12 inches of clarity it may be smart to provide aeration to the pond to reduce the possibility of a fish and aquatic animal die off. When sunlight can reach deeper into the water column the probability of increase aquatic weed growth happens. This condition can be offset by increasing the soil turbidity or by adding a dye colorant. Water clarity changes are a good indicator of a process in action.