When water is not clear in a pond it is generally caused by one of two things, either suspended solids or planktonic
algae. Suspended solids are simply small bits of dirt, clay or other non-living substances that are so small they do not naturally settle out of the water quickly. Planktonic algae on the other hand is very small algae that does not live in large mats. Both can make it hard to see through your water which can limit your enjoyment of the pond. Although both cause the same issue visually, solving the problem will depend on the cause of the issue.
Firstly, let’s explore the solution for suspended solids. There are many sources of suspended solids, and they can include surface run-off, koi or carp stirring up debris, a newly filled pond or excessive water movement. Surface run-off generally occurs when there are exposed soil, mulch or gardens around and uphill from the pond. When a heavy rainfall occurs, this dirt is washed into the pond causing problems. This can be solved by changing the grade around the pond to prevent water following into the pond after passing over exposed soil or adding an area of plants near the edge to catch the soil.
Koi, goldfish, carp and other bottom feeding fish can also cause problems in an earth bottom pond by continuously digging and stirring up clay. The best solution for this would be to remove the problematic species of fish and replace them, if fish are desired, with native minnows and other species.
Suspended solids are often seen in new clay lined ponds as clay is extremely slow to settle out as it is so small, it can in fact take years for it to clear on its own. In this instance I would recommend considering flocculant. Flocculants are products that clump together small particles which makes them heavy enough that they sink. Metafloc is a great option for a flocculant that will rapidly clear his type of clarity issue.
The last main cause of suspended solid is rapid water movement. This can be caused by a variety of sources including a waterfall and aeration diffuser. With waterfalls, simply adding a liner covered with stones at the base will not only prevent suspended solids but also erosion at the base of the waterfall that may cause future problems. In some instances, generally newly installed pond, the clay at the bottom of a pond is loose enough that the water movement caused by air diffusers will stir up debris. In these cases, the best solution would be to suspend the air diffusers on floats a couple of feet of the bottom. This will still allow you to fully benefit from the aeration without causing water clarity issues.
The second main cause of water clarity issues is planktonic algae. We discuss management strategies for planktonic algae in “Stopping algae before it starts” on page 6.
If you are unsure which of these issues is causing you clarity issues, we would be happy to examine a water sample for you and test it for nutrient levels.
