To Dye or Not to Dye

Open water venues are often criticised when people notice the water has been “dyed blue” or treated in some way. The assumption is usually that it is cosmetic designed to make the lake look cleaner or more appealing for social media photos. In reality, at many managed swim venues, water dye is used as part of a wider pond and lake management strategy focused on safety, ecology and swimmer health.

For venues that support regular swimming, particularly during warmer months, unmanaged weed growth can quickly become a genuine operational and health issue rather than just an aesthetic one.

Aquatic dyes work by limiting the amount of sunlight penetrating deeper into the water. Less light means reduced photosynthesis, which in turn slows the growth of submerged weeds and algae. The goal is not to sterilise the lake or create an artificial environment. It is usually about keeping ecological balance within a body of water that is being actively used by people.

Why Weed Control Matters for Open Water Swimming

Weeds are not inherently “bad.” Healthy aquatic plant life supports biodiversity, oxygenates water and creates habitats for insects, fish and amphibians. The problem comes when growth becomes excessive in managed swim environments.

Heavy weed growth can:

• Reduce safe swimming areas

• Create entanglement risks for inexperienced swimmers

• Trap sediment and organic material

• Increase stagnant zones in shallow areas

• Accelerate algae blooms during warm weather

• Make water quality harder to manage consistently

Warm, nutrient-rich lakes with high sunlight exposure can see explosive growth during spring and summer. Once established, some aquatic weeds become extremely difficult and expensive to control mechanically.

For swimming venues, the issue is often operational rather than visual. Thick weed beds increase maintenance costs, reduce usable water space and can contribute to poor swimmer experience and safety concerns. No one likes to be touched by the monsters beneath.

The Link to Swimmer’s Itch

One of the lesser-known reasons some venues actively manage weed levels is to reduce the likelihood of swimmer’s itch.

Swimmer’s itch is a skin irritation caused by microscopic parasites released by certain freshwater snails. These parasites mistakenly burrow into human skin, causing itchy red spots or rashes. While not usually dangerous, it can be uncomfortable enough to put people off open water swimming entirely.

The important ecological detail is this:

• Freshwater snails thrive in shallow, warm, heavily vegetated water

• Dense aquatic weed creates ideal habitat for them

• More snails can increase the lifecycle opportunities for the parasites involved

Reducing excessive vegetation does not “eliminate” swimmer’s itch entirely, but it can help reduce the environmental conditions that allow it to become more prevalent.

This is one reason many professionally managed swim venues focus heavily on circulation, weed management, water quality and ecological balance rather than simply letting lakes naturalise unchecked.

We thankfully we don't currently experience this issue so its really important that we keep it that way.

Pros of Using Lake Dye

Reduced Weed Growth

The primary benefit is slowing submerged weed growth naturally through light reduction rather than relying solely on aggressive chemical treatment or constant mechanical cutting.

Improved Swimming Conditions

Less dense vegetation creates clearer swim routes and safer conditions for less experienced swimmers.

Potential Reduction in Swimmer’s Itch Risk

By discouraging the heavily vegetated shallow environments favoured by snails, venues may reduce some of the environmental conditions linked to swimmer’s itch.

Lower Algae Pressure

Reducing sunlight penetration can also help limit certain algae blooms, particularly during hotter weather.

Reduced Mechanical Disturbance

Without dye, some venues may need repeated weed cutting or dredging, which can disrupt lake ecosystems more aggressively.

Cons and Trade-Offs

Reduced Light for Aquatic Plants

The obvious trade-off is that beneficial aquatic plants are also affected. Overuse can reduce biodiversity if not carefully managed.

Public Perception

Some swimmers dislike the appearance or assume the water is “artificial” or chemically unsafe, even when dyes are specifically designed for aquatic environments.

Ecological Balance Can Shift

Every intervention changes an ecosystem. Responsible venues monitor water quality, oxygen levels and biodiversity carefully rather than relying on one single solution.

At Yoke Hill we dye the water and we are very aware its a fine line, its important we protect our lake and its eco system, the objective is usually not to create a pristine ornamental lake. It is to maintain a stable, healthy environment that supports both ecology and safe for all our swimmers and dippers.