Avoiding a six-figure dredging project and preventing major fish kill
How a German municipality avoided a six-figure dredging project while restoring water quality and preventing a major fish kill.
Key Facts
- Project:
- Schwanenweiher Park Pond
- Location:
- Rhineland Palatinate, Germany
- Type & Size:
- Freshwater Municipal Pond, 1 Hectare
- Problem:
- Foul odor, oxygen depletion, sludge formation, fish kills
- Product Applied:
- SchlixX Plus
- Results:
- Sludge reduced on average by 30 cm (11.81 in), fish kill prevents, oxygen content optimized and stabilized and odor pollution reduced
Project Overview
A science-led nutrient management strategy
As part of its Town Center development, the City of Early, Texas set out to transform a former agricultural pond into a 7-acre recreational fishing lake designed to serve as a long-term community asset.
Shortly after construction and refill, the lake experienced significant water quality challenges driven by elevated nutrient levels and rapid algae growth.
Oase Water Technology, working alongside Texas Pro Lake Management, was engaged to design and deliver a science-led nutrient management strategy focused on long-term system stability.
“We wanted to do something different than just build another park. We envisioned turning this into a fishing lake that could really become the heart of the community.” – Tony Aaron, City Administrator, City of Early
The Challenge
Although the lake itself was newly constructed, it was filled using existing river water. This introduced high nutrient loads into a system without an established biological foundation, creating ideal conditions for algae growth.
Key challenges included:
Elevated phosphorus concentrations
Imbalanced nitrogen dynamics
Rapid algae development and poor water clarity
Limited microbial activity in newly formed sediments
A requirement for solutions safe for public use
The Traditional Approach
Dredging appeared to be the only viable option.
However, when costs were assessed, the project quickly became financially challenging. Dredging alone was expected to run into six figures, with additional six-figure costs associated with sediment handling and disposal.
For a relatively small municipal pond, the investment was difficult to justify.
The City therefore began exploring alternative approaches that could address the underlying causes of decline without the disruption and expense associated with large-scale dredging.
The Solution & Results
The chosen approach combined SchlixX Plus and PeriDox.
The treatment works by combining oxygen-releasing chemistry with specialised biological components that support the breakdown of organic material while helping stabilise nutrient dynamics within the pond.
Approximately one tonne of SchlixX Plus was applied across the water body.
Shortly after treatment, an unexpected weather shift created a new challenge. Following a period of warm conditions, cooler and darker weather significantly reduced photosynthetic activity within the pond.
As oxygen production declined and biological demand remained high, a fish mortality event began to develop.
To prevent further losses, PeriDox was deployed as an emergency response measure, rapidly restoring dissolved oxygen levels and preventing the pond from tipping into a full ecological collapse.
The intervention proved critical.
Despite an estimated fish population of between 150,000 and 250,000 fish, losses were limited to only a few hundred individuals.
Subsequent monitoring demonstrated significant improvements throughout the pond:
Approximately 55% reduction in accumulated sediment
Improved dissolved oxygen conditions
Significant reduction in odour issues
Improved overall water quality
Stabilised fish populations
Restoration of valuable water volume
Perhaps most importantly, the remaining sediment was transformed from a black, foul-smelling sludge into a healthier, more stable substrate with an earthy appearance and odour.
Long-term impact
What began as an urgent environmental issue quickly became a public concern, attracting attention from local residents, media outlets, and municipal stakeholders.
By combining proactive sediment management with rapid oxygen intervention, the City of Landau was able to avoid a costly dredging programme, prevent a major fish kill, and restore confidence in one of its valued public spaces.
Today, Schwanenweiher Pond continues to serve residents as a place for recreation and wildlife, supported by a more stable aquatic environment and improved long-term water quality.
Request a free consultation
Complete the form and one of our specialists will contact you to arrange a convenient time for a discussion.