Is string algae bad for a pond?

While filamentous algae may not be visibly appealing, it can provide some benefit to the pond when present in moderate amounts. It is a food source for invertebrates, protozoans, and fish.

If a bloom is covering the majority of the surface, this shows that excess nutrients are present. It is important to reduce nutrients levels within the pond or lake.

An algae bloom can create dangerous conditions for aquatic life in ponds and lakes. Algae produce oxygen through photosynthesis during daylight hours. They also consume oxygen 24 hours a day. At night, the algal bloom can use all of the available dissolved oxygen in the water causing a fish kill.

Similarly, using an algaecide creates dead plant matter that consumes oxygen and can also cause a fish kill. Pond Aeration can reduce the stress on aquatic life and limit the risk of fish kills.

Planktonic

Pond managers commonly refer to planktonic algal blooms as green water or pea soup. These single-celled Diatoms float freely throughout the pond. Coloration of planktonic forms can be green, yellow, blue-green or brown.

Planktonic blooms can be a sign of a serious imbalance in water. If the visibility in to the water column is less than 18 inches, you should take steps to improve water conditions.

Planktonic blooms produce oxygen during the day and consume oxygen at night. A heavy planktonic bloom can result in a fish kill from oxygen uptake at night. These kills can also occur when there are consecutive overcast days. Without sun, planktonic blooms consume oxygen during the day instead of producing it.

Chara & Nitella

Chara and nitella are types of macro-algae. They are commonly misclassified as submerged weeds but are forms of algae. People also know Chara as muskgrass because of its strong odor.

Chara produces stems with leaves growing in whorls around the stems. There is a gritty calcified outer coating. Chara has a skunk-like odor. It is typically found in hard water.

Nitella has similar looking growth to chara but lacks the gritty calcified coating and has no odor. Nitella, typically found in acidic or soft water, is also more delicate than chara.

There is no root system with macroalgae forms.

Algae Control for Ponds

Effective controls for algal blooms include pond algaecides, pond dye, and beneficial bacteria to reduce excessive nutrients in the water.

Granular algaecides can be utilized to prevent and treat filamentous blooms by focusing on the growth at the bottom of the pond. After the mats have begun to float to the surface, liquid algaecides should be used to gain control.

Pond dye is an effective control when used consistently to block sunlight from reaching the pond bottom.

Reducing excess Nitrogen and Phosphorus in the water column is also a very effective preventative. Beneficial bacteria digest Ammonia, Nitrate, and Nitrite in the water and release it to the atmosphere as Nitrogen gas.