What Kind of Algae Is in Your Pond? A Guide to Common Algae Types

Algae are a normal and essential part of freshwater ecosystems. Many types play critical ecological roles, producing oxygen and forming the base of the aquatic food web. But when conditions shift out of balance, especially due to excess nutrients like phosphorus or nitrogen, algae can grow rapidly, overwhelming your pond and turning it into a murky, green mess.

As we move into fall, many pond owners expect algae to fade away. But in the Southeast, shorter days don’t always mean cooler weather. Warm temperatures can linger well into autumn, allowing algae to continue thriving. Understanding what type of algae is present, and why it persists, helps you take proactive steps to keep your pond clear and healthy.

1. Planktonic Algae (Free-Floating Algae)
Planktonic algae are microscopic organisms suspended throughout the water column, often causing the green, cloudy appearance associated with algae blooms.

Management Tips:

• Reduce nutrient inputs, especially phosphorus. Avoid using phosphorus-based fertilizers near the water and redirect stormwater runoff.
• Plant native shoreline vegetation to filter nutrients before they enter the pond.
• Use phosphorus-binding products to lock up available nutrients in the water.
• Algaecides, when needed, should always be applied by a licensed professional and paired with aeration or biological support to prevent oxygen depletion.

2. Filamentous Algae (String Algae or Pond Scum)
This algae grows in long, hair-like strands and often floats to the surface in dense mats. It thrives in shallow, nutrient-rich areas and is one of the most common complaints among pond owners—even in the fall when water stays warm.

Management Tips:

• Manually remove early growth to reduce nutrient recycling as it decays.
• Install aeration, either diffused aeration or a floating fountain, to improve circulation and oxygen levels.
• Apply beneficial bacteria to break down organic sludge and limit nutrients.
• For heavy infestations, apply a targeted algaecide through professional service and follow up with long-term strategies like nutrient and circulation management.

3. Blue-Green Algae (Cyanobacteria)
Though technically a bacteria, cyanobacteria behave like algae and are responsible for many harmful algal blooms (HABs) that may release toxins dangerous to people, pets, and wildlife.

Management Tips:

• Prevent nutrient loading from fertilizers, animal waste, and nearby septic systems.
• Use aeration to reduce stagnant, low-oxygen zones where HABs thrive.
• Apply phosphorus-binding agents to remove key nutrients from the water.
• Only apply algaecides under professional guidance. Proper identification of the cyanobacteria type and risk is essential.

Algae Identification and Monitoring
Proper identification is crucial to determining the right management approach:

• Use visual cues such as color, growth form, and location in the waterbody.
• Conduct regular water testing for phosphorus, nitrogen, and oxygen levels.
• Perform seasonal monitoring to catch potential problems early, fall is an excellent time to evaluate nutrient loads before cooler weather sets in.

A Proactive Approach to Algae Control
Algae are a natural part of a healthy pond. But when nutrient levels become unbalanced, algae can grow rapidly and disrupt water quality, appearance, and aquatic life.

Algaecides, when applied by licensed professionals, are one effective tool, but they should be part of a larger, integrated lake management program. The key to sustainable algae control is proactive pond management. Regular monitoring, nutrient reduction, and aeration build the foundation of a healthy aquatic system, minimizing the need for reactive treatments and keeping your pond beautiful, healthier, and more enjoyable through fall and beyond.

About Aqua Services, A Jones Lake Management Partner

Since 1983, Aqua Services has been a trusted leader in lake and pond management, delivering scientifically backed solutions to create and maintain healthy, balanced, and beautiful waterbodies. As a Jones Lake Management Partner, our team specializes in a full range of services to include algae and aquatic weed control, aeration systems, water quality monitoring, fisheries management, hydraulic dredging, invasive species control, and shoreline restoration. We work with HOAs, municipalities, golf courses, and private lake owners throughout Alabama, Arkansas and Georgia to maintain balanced and thriving aquatic environments through science-based and sustainable management practices.