Cleaning is an essential part of fish cage maintenance.
A clean net can provide:
Better water exchange
Lower hydrodynamic drag
Improved oxygen movement
Easier inspection
More stable cage performance
However, cleaning is not completely risk-free.
If the wrong tools, pressure, angle, timing, or technique are used, the cleaning process can damage the net itself.
The damage may include:
Surface abrasion
Frayed fibers
Loose knots
Distorted mesh
Damaged seams
Weakened coatings
Broken twine
This creates an important maintenance paradox:
Cleaning can protect a fish cage net, but aggressive cleaning can also shorten its service life.
For aquaculture operators, the goal is not simply to remove all fouling as quickly as possible.
The goal is to remove fouling while preserving the net’s structural integrity.
Fish cage nets are continuously exposed to marine growth.
Common fouling may include:
Algae
Slime
Barnacles
Mussels
Tubeworms
Other marine organisms
As fouling accumulates, it reduces the effective mesh opening.
This can increase:
Water resistance
Net weight
Cage deformation
Structural load
Cleaning helps restore more normal net performance.
Most cleaning methods apply some form of mechanical action.
This may involve:
Water pressure
Brushing
Scraping
Rotating cleaning heads
Net movement
The cleaning force must be strong enough to remove fouling.
But if that force exceeds what the net can safely tolerate, the twine may also be damaged.
High-pressure water jets are widely used because they remove fouling quickly.
However, excessive pressure can damage the net surface.
A concentrated jet may:
Split filaments
Fray twisted strands
Loosen surface fibers
Damage knots
The risk increases when the nozzle is placed too close to the mesh.
The closer a pressure-washing nozzle is to the net, the more concentrated the force becomes.
A safe pressure at one distance may become damaging when used only a few centimeters away.
Operators should control:
Nozzle distance
Jet angle
Time spent on one point
Holding the jet in one place for too long can create localized damage.
A jet directed straight into the net may produce more local loading than a controlled angled spray.
Direct impact can push the mesh strongly and concentrate force on:
Twine
Knots
Seams
A suitable cleaning angle may reduce unnecessary stress while still removing fouling.
Small-mesh netting contains more twine and more intersections within a given area.
It may also hold more fouling.
Operators may be tempted to increase cleaning pressure.
But higher pressure can increase the risk of:
Mesh distortion
Twine damage
Knot movement
Cleaning settings should match the actual net specification.
Lightweight netting may not tolerate the same cleaning force as heavy-duty cage netting.
Thin twine has less material available to absorb:
Abrasion
Impact
Bending
A cleaning method suitable for thick offshore netting may be too aggressive for a lighter coastal cage.
A new net may have high remaining strength and flexibility.
An older net may already be weakened by:
UV exposure
Abrasion
Repeated loading
Previous cleaning
Material aging
Using the same cleaning settings on both nets may produce very different results.
Cleaning procedures should consider net age and condition.
Manual or mechanical brushes may be used to remove slime and attached organisms.
If the bristles are too hard, they can scrape the twine surface.
Repeated brushing can gradually:
Polish the material
Thin fibers
Damage twisted strands
Loosen knots
The damage may not be visible after one cleaning cycle.
It can accumulate over time.
Not all brushes are suitable for all net types.
A stiff metal or very hard plastic brush may remove fouling quickly but also damage polymer twine.
Softer cleaning tools may require more time but reduce abrasion.
The correct balance depends on:
Net material
Fouling type
Net age
Coating condition
Even moderate brushing can become harmful when repeated too frequently.
Each cleaning cycle creates:
Contact
Bending
Friction
Over many cycles, these actions may contribute to localized fatigue.
Maintenance frequency should be based on actual fouling conditions rather than a fixed habit alone.
Scrapers or blades may be used against hard fouling.
These tools can be dangerous near flexible mesh.
A small slip may:
Cut twine
Open a mesh
Damage a knot
Slice a seam
Sharp tools should be used only with strict control, if used at all.
Barnacles and mussels may attach strongly to the net.
When they are removed, they may not separate cleanly.
They can pull, scrape, or twist the twine.
The cleaning force is therefore transferred into the net structure.
Heavy hard-fouling removal is more damaging than removing soft slime early.
Light fouling may be removed with relatively gentle methods.
Heavy mature fouling may require:
Higher pressure
Harder brushing
More repeated passes
This increases the risk of net damage.
A planned cleaning schedule can reduce the need for aggressive treatment.
Automated or remotely operated cleaning systems can improve efficiency.
However, they also create mechanical contact with the net.
Possible risks include:
Excessive pressure
Repeated passes
Contact with seams
Catching on damaged mesh
The equipment must be adjusted to the net and cage design.
Moving cleaning equipment may include:
Wheels
Brushes
Rotating heads
Guides
If part of the machine catches a mesh opening, it may pull the twine.
This can create:
Distortion
Broken strands
Enlarged openings
Damaged or loose mesh is especially vulnerable.
A cleaning machine may press against the net to maintain contact.
If the load is concentrated, the mesh beneath the device may experience:
High local tension
Stretching
Abrasion
The equipment should distribute contact force as evenly as practical.
Knots are raised and complex areas.
Brushes and water jets may strike them more strongly than straight twine.
Repeated cleaning can increase wear:
At the knot
Immediately beside the knot
In knotted cage nets, knot condition should be inspected after cleaning.
Large fish cage nets often include joined panels or seams.
These areas may contain:
Additional twine
Different stiffness
Repair material
Reinforcement
Cleaning equipment may behave differently when crossing a seam.
It can catch or apply uneven pressure.
Seams should be treated as high-risk cleaning zones.
A repaired section may not have exactly the same:
Flexibility
Mesh geometry
Surface profile
as the original net.
Cleaning tools may catch the repair or pull on the boundary.
The patch may remain intact while the older net beside it tears.
Cleaning may move the net relative to:
Border ropes
Cage frames
Rings
Clips
If the net is pushed against these components, abrasion can increase.
The damage may occur away from the cleaning head itself.
Pressure washing or brushing pushes the flexible mesh.
This movement may press the net against:
Sharp bolts
Rough frames
Damaged clips
Hard marine growth
The cleaning force can therefore create secondary abrasion.
Inspect nearby structures before cleaning begins.
A highly tensioned net has less freedom to move away from the cleaning force.
Pressure may be concentrated directly into the twine.
A moderately tensioned net may absorb some movement.
However, a very loose net can also fold and catch cleaning equipment.
Balanced tension is important.
If the net is too loose, it may:
Wrinkle
Fold
Flap
during cleaning.
Loose folds may become trapped in brushes or rotating equipment.
This can cause sudden pulling and torn mesh.
Repeated pressure can temporarily or permanently change mesh shape.
The mesh may become:
Elongated
Compressed
Twisted
This can affect:
Fish containment
Water exchange
Load distribution
After cleaning, check whether the mesh returns to its normal geometry.
Some aquaculture nets may use:
Protective coatings
Resin treatments
Antifouling systems
Aggressive cleaning can remove or damage these layers.
This may reduce:
Surface protection
Antifouling performance
Future durability
Cleaning methods should be compatible with the applied treatment.
A treated net may still require maintenance.
But operators should not assume the coating is mechanically indestructible.
High pressure or scraping may damage the treatment before the underlying twine is visibly harmed.
The treatment supplier’s instructions should be followed where available.
Sometimes damage found after cleaning was not caused by the cleaning process.
The fouling may have hidden:
Frayed strands
Broken knots
Small tears
Old abrasion
Once the growth is removed, the defect becomes visible.
This is why before-and-after inspection is important.
Even if cleaning did not create the original weakness, the applied force may cause a weakened strand to break.
For example, an old abraded twine may survive under normal loading but fail when struck by a strong water jet.
The cleaning event becomes the final trigger.
When a section is pushed or pulled during cleaning, load can move toward:
Corners
Attachments
Seams
Border ropes
The actual failure may occur nearby rather than directly beneath the tool.
This is another reason to inspect the wider area.
If pressure is always applied from the same direction, the net may repeatedly deform toward one side.
This can increase contact with structural components behind the mesh.
Where practical, cleaning strategy should consider how force moves through the cage.
Cleaning does not occur in a static environment.
The net may already be moving because of:
Current
Waves
Cage motion
The cleaning force is added to these environmental loads.
A method that is safe in calm water may become more damaging under strong movement.
Offshore cages often experience:
Higher waves
Stronger current
More dynamic cage movement
Cleaning equipment may be harder to control.
Net contact can become less predictable.
Offshore maintenance planning should include suitable weather and current conditions.
Manual cleaning may involve divers or farm workers.
Damage can occur when:
Tools are dropped
Hoses catch the mesh
Workers pull on the net
Fins or equipment rub against it
Training and careful equipment management reduce these risks.
Pressure-washing hoses may move against:
Netting
Seams
Ropes
during cleaning.
Repeated hose contact can create abrasion, especially when sand or hard fouling is trapped between surfaces.
Hose routing should be controlled.
Operational ropes or cables may catch on:
Knots
Repairs
Clips
Loose twine
Pulling them free can enlarge existing damage.
Before cleaning, inspect and organize equipment routes.
Cleaning hard fouling may release:
Shell fragments
Sand
Grit
These particles can become trapped between the tool and the net.
They act like abrasive material.
Rinsing and controlled tool pressure can help reduce this effect.
Brushes and equipment may collect:
Shell pieces
Wire
Sharp debris
If not cleaned, the tool itself becomes abrasive.
Cleaning equipment should be inspected before and during use.
Keeping a net perfectly clean at all times may sound ideal.
But unnecessary frequent mechanical cleaning increases cumulative contact.
A maintenance plan should balance:
Fouling control
Water exchange
Mechanical wear
The best schedule depends on site conditions and operating requirements.
Avoiding cleaning completely is not the answer.
Heavy fouling increases:
Drag
Weight
Deformation
Structural loading
This can damage the cage in a different way.
The correct strategy lies between:
Too Aggressive and Too Infrequent
Soft slime may respond to gentle washing.
Hard shell growth may require a different approach.
Using one method for every type of fouling can result in:
Ineffective cleaning
Unnecessary net damage
Identify the fouling before choosing the tool.
Before cleaning, consider:
Net material
Twine diameter
Mesh size
Knot type
Coating
Net age
The same settings should not automatically be used across every cage.
Before cleaning the whole cage, try the selected method on a small controlled area.
Then inspect for:
Fraying
Coating loss
Mesh distortion
Knot damage
If damage appears, adjust the method before continuing.
A practical principle is:
Use Enough Force to Remove Fouling, but No More Than Necessary.
Start with:
Lower pressure
Greater nozzle distance
Softer brushes
Increase cleaning intensity only when required.
Repeatedly cleaning one stubborn spot concentrates mechanical action.
This can overwork the same twine.
Instead of holding pressure continuously, use controlled passes and reassess the area.
If the mesh is:
Stretching excessively
Folding into the tool
Pulling away from attachments
stop and adjust the procedure.
Visible abnormal movement is an early warning.
Known tears, loose knots, and old repairs should be handled carefully.
Aggressive cleaning near these areas may enlarge the damage.
They may require:
Lower pressure
Manual inspection
Repair before normal cleaning resumes
A pre-cleaning inspection should identify:
Existing holes
Weak seams
Loose attachments
Sharp structures
Heavy hard fouling
This allows the team to plan the cleaning method and avoid high-risk areas.
After fouling is removed, check:
Twine surface
Knots
Seams
Repairs
Corners
Attachments
Many defects are easier to see on a clean net.
Maintenance records should include:
Cleaning date
Method used
Equipment settings
Damage found
Repairs completed
This helps determine whether certain cleaning methods are associated with repeated damage.
If damage appears only in areas cleaned by one:
Machine
Tool
Operator
Pressure setting
the cleaning process may be contributing.
Comparing zones can help identify the cause.
Operators should know how to identify:
Fraying
Flattened twine
Loose knots
Distorted mesh
Coating loss
Early recognition allows cleaning to be adjusted before a hole develops.
A professional cleaning procedure may define:
Approved equipment
Pressure range
Nozzle distance
Cleaning angle
Inspection steps
High-risk zones
Standardization reduces operator-to-operator variation.
Do not treat every cage net the same.
Older and repaired nets may need:
Lower pressure
Softer tools
More frequent inspection
Slower cleaning
Condition-based maintenance is safer than one universal setting.
Some farms clean nets in place.
Others remove and exchange them.
Removing a net may allow:
Better inspection
Controlled cleaning
More thorough repair
But net handling also introduces additional stress.
The best approach depends on cage design, farm equipment, and maintenance capacity.
A removed net may be damaged if it is:
Dragged on concrete
Scraped across metal
Folded around sharp edges
Cleaned with unsuitable machinery
Moving the net onshore does not eliminate cleaning risk.
Handling procedures remain important.
After cleaning, the net may be:
Dried
Folded
Stored
Reinstalled
Poor handling can create:
Creases
Abrasion
Contamination
UV exposure
Cleaning should be viewed as one part of a full maintenance process.
If tears repeatedly appear after cleaning, do not assume the net is simply low quality.
Review:
Pressure
Tools
Equipment contact
Net age
Fouling severity
Operator technique
The root cause may be the maintenance process.
Heavy-duty netting may tolerate more mechanical contact.
But it can still be damaged by:
Sharp tools
Excessive pressure
Repeated abrasion
Stronger material provides a larger safety margin, not unlimited resistance.
The purpose of net cleaning is to restore performance without creating new weaknesses.
A successful cleaning program should improve:
Mesh openness
Water exchange
Inspection visibility
while minimizing:
Twine abrasion
Knot damage
Mesh distortion
Coating loss
Before cleaning:
✔ Confirm the net material and twine size
✔ Inspect existing tears, repairs, and weak seams
✔ Identify soft or hard fouling
✔ Check nearby frames, ropes, and sharp structures
✔ Select suitable pressure and tools
✔ Test the method on a small area
During cleaning:
✔ Maintain appropriate nozzle distance
✔ Avoid excessive pressure and repeated passes
✔ Watch for abnormal mesh movement
✔ Keep hoses and equipment from catching the net
✔ Reduce intensity near seams and repairs
After cleaning:
✔ Inspect twine, knots, seams, and borders
✔ Check for fraying or distorted mesh
✔ Confirm repairs remain secure
✔ Record the method and any damage found
✔ Repair defects before returning the cage to normal service
Net cleaning is essential for controlling:
Fouling
Drag
Weight
Water-flow reduction
But cleaning can accidentally damage fish cage nets when operators use:
Excessive water pressure
Hard brushes
Sharp scrapers
Poorly adjusted robots
Repeated aggressive cleaning
Unsuitable methods for old or coated netting
The safest principle is:
Use the Least Aggressive Method That Removes the Fouling Effectively.
A reliable cleaning program combines:
Correct Tools + Controlled Pressure + Suitable Timing + Trained Operators + Before-and-After Inspection
For aquaculture farms, the net should not only look cleaner after maintenance.
It should remain structurally sound enough to contain fish and perform safely in real marine conditions.
At PL Fishery, we manufacture PE fish cage nets, aquaculture netting, fishing nets, marine ropes, chicken nets, and customized netting products for different fish-farming environments.
Need to buy, replace, or customize fish cage nets for your mesh size, cage dimensions, fouling conditions, cleaning method, reinforcement, or marine environment? Contact PL Fishery with your project requirements, and our factory team can help develop a suitable netting specification for your application.https://plfishery.com/
