Keeping water clear in decorative ponds with valuable fish is not only an aesthetic challenge.
In closed water systems, microorganisms and algae can multiply quickly because nutrients continuously circulate through filtration loops. If the balance is disturbed, the water can become cloudy, green and unsuitable for long-term fish keeping.
A fish pond complex with two large artificial reservoirs faced this exact problem.
The solution was not to add chemicals directly into the ponds, but to treat the circulating water outside the main habitat using ultraviolet technology.
The pond system
The facility included two closed-loop ponds connected to filtration systems.
The parameters were:
Pond 1
volume: approximately 1,800 m³;
filtration flow: 450 m³/h;
inhabitants: large sturgeon family fish, including beluga.
Pond 2
volume: approximately 800 m³;
filtration flow: 350 m³/h;
inhabitants: carp.
Both systems used:
mechanical filtration;
biological filtration;
polypropylene storage tanks;
continuous water circulation.
The UV equipment had to be integrated into the existing filtration loop without changing the pond structure.
The problem: uncontrolled algae growth
The main issue was intensive water "blooming".
This happens when algae and microorganisms reproduce faster than the filtration system can remove them.
Typical symptoms include:
green water tint;
reduced visibility;
increased organic load;
additional stress for aquatic organisms.
Previous attempts to solve the problem with ozone treatment did not provide stable results.
The main difficulties were:
the need for constant monitoring;
sensitivity of the equipment;
unstable operation results.
Because the ponds contained valuable fish, the treatment method had to work without creating additional risks for the ecosystem.
Why treat the water outside the pond?
Direct UV exposure inside a pond is not usually practical.
The radiation must affect microorganisms, but the fish and the surrounding environment should remain unaffected.
The chosen approach was therefore:
water leaves the pond through the filtration system;
it passes through treatment tanks;
UV modules disinfect the circulating water;
treated water returns to the pond.
This creates a controlled treatment zone separated from the living environment.
Submersible UV modules inside storage tanks
The existing polypropylene tanks became the installation point for the UV equipment.
Instead of adding an external reactor with new piping, submersible modules were installed directly inside the tanks.
The configuration used:
UVL Mod 19180 modules
Technical parameters:
lamp power: 172 W;
UV output: 55 W;
wavelength: 254 nm;
lamp type: ozone-free amalgam;
service life: up to 16,000 hours;
quartz protective sleeve;
sealed fluoroplastic mounting assembly;
electronic ballast with operating indication.
The total installation included:
24 modules for the first pond;
16 modules for the second pond.
Why amalgam UV lamps were selected
Large outdoor and semi-outdoor water systems have changing operating conditions.
Water temperature can vary significantly between seasons, which affects conventional low-pressure UV lamps.
Amalgam lamps are often used in situations where stable UV output is required over a wider operating range.
Their advantages include:
high UV efficiency;
stable output;
long operating life;
suitability for continuous operation.
Installation challenges
The main engineering task was not simply installing lamps.
The equipment had to work inside existing tanks without redesigning the filtration system.
The installation required consideration of:
tank geometry;
module placement;
cable routing;
maintenance access;
quartz sleeve cleaning.
The modules were fixed directly through sealed mounting points, while the power supplies were located in protected areas outside the wet zone.
Maintenance considerations
UV systems do not remove the need for maintenance.
Over time, deposits can form on quartz sleeves, reducing the amount of radiation reaching the water.
To maintain performance, the sleeves need periodic inspection and cleaning.
This is especially important in systems with:
high organic loading;
biological filtration;
warm water;
intensive fish stocking.
Why continuous operation matters
Algae control is usually not a one-time treatment.
If microorganisms are reduced today but the circulation system stops treatment, the population can begin growing again.
Continuous operation helps maintain a more stable microbial balance in the circulating water.
What this project shows
Large decorative ponds with fish are essentially small engineered ecosystems.
Maintaining water quality requires balancing:
biological filtration;
circulation rate;
organic load;
fish population;
microbial activity.
UV treatment is not a replacement for filtration, but it can become an important part of a complete water management system.
In this case, installing UV modules into the existing circulation loop allowed the water to be treated without adding chemicals directly into the ponds and without changing the existing filtration architecture.
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