What’s Hiding Below?

Common Underwater Weeds and Why They Matter

Not all aquatic weeds float on the surface. Some of the most disruptive species grow entirely beneath the waterline, where they can spread unnoticed - until they start affecting water flow, oxygen levels, and native wildlife.

Here are three of the most common submerged aquatic weeds found in UK waterbodies and why they need to be managed.

Canadian Pondweed (Elodea canadensis)

This invasive weed is fully submerged, with slender green leaves arranged in whorls along the stem. It thrives in slow-moving or still water and quickly forms dense underwater mats.

Why it matters:

• Reduces oxygen available to fish and aquatic life
• Crowds out native plants
• Can block intakes, culverts and irrigation pipes

Curled Pondweed (Potamogeton crispus)

Easily identified by its crinkled, ribbon-like leaves, this species grows rapidly early in the season and can form a thick layer just below the surface.

Why it matters:

• Restricts water movement
• Impacts biodiversity by outcompeting other submerged plants
• Can rebound quickly without consistent maintenance

Nuttall’s Pondweed (Elodea nuttallii)

Often confused with Canadian pondweed, Nuttall’s is even more vigorous. It has finer leaves and a softer texture, but it spreads just as fast - and can dominate shallow lakes and ditches.

Why it matters:

• Forms tangled growth that can clog waterways
• Inhibits fish movement and spawning
• Creates low-oxygen conditions that harm aquatic ecosystems

Why Submerged Weeds Matter

Just because you can’t always see them, doesn’t mean they’re not causing problems. Left unmanaged, submerged aquatic weeds can:

• Lower water quality
• Disrupt natural habitats
• Increase flood risk
• Cause mechanical damage to pumps and intakes

At The Aqua Contractor, we use mechanical weed removal to clear and control submerged weeds without the use of chemicals. It’s a safer, more sustainable option for long-term aquatic health.

Need Help with Submerged Weeds?

We offer on-site assessments and free, no-obligation quotes. If your pond, lake or waterway is showing signs of reduced flow or weed build-up, our team can help.