Mostly hard fouling, not waterline slime: independent field tests found that ultrasonic antifouling did not prevent slime and green algae at the waterline, while it did reduce barnacles and other hard growth, and Lamers System Care does not promise an algae-free waterline with SMART FLOW. Lamers System Care uses SMART FLOW where the signal can travel through stiff, permanently wetted structure — box coolers, sea chests and piping, and on hulls usually together with a hard coating — to disrupt the biofilm that mussels and barnacles need to settle.
Short answer, with the evidence
- Waterline slime and algae: not stopped. The Endures field test for HISWA (report RPT19027, salt-water location Bruinisse) concluded for both ultrasonic systems tested that “they are not able to prevent algal and slime fouling at the waterline”, with green algal filaments of 10–15 cm along the waterline later in the season.
- Slime below the waterline: lighter, not gone. In Practical Boat Owner’s Hamble test none of the systems produced a completely clean boat, but on the ultrasonic boats “the slime was noticeably lighter and easier to remove”; all boats, with or without ultrasound, had green weed at the waterline.
- Hard fouling: where ultrasound does best. Endures notes that “against other types of marine fouling the systems do work”; PBO reports that the systems are said to be more effective against barnacle growth; Nordkyn Design’s long-running trial on an aluminium yacht found hard growth such as barnacles eliminated even where paint was gone.
Why the waterline is the weak spot
Ultrasonic systems put vibration into the structure; PBO describes how “the ultrasonic waves propagate through the hull laminate”. The waterline is where that structure meets air, sunlight and splash, which is exactly where green algae grow fastest. Nordkyn Design calls waterline slime and algae “a known limitation of ultrasonic antifouling systems” and suggests the energy may not reach algae close to the free surface — while barnacles still did not develop there. Endures adds that the working principle is still not fully understood and refers to RIVM’s conclusion that sound scientific evidence is lacking.
Where SMART FLOW is used instead
Lamers System Care designs SMART FLOW around the biofilm stage: controlled high-frequency pulses create micro-vibrations in the material so micro-organisms attach less easily, and without that biofilm larger organisms such as mussels struggle to settle. That works best on stiff material that carries sound (steel, aluminium, polyester) and on surfaces that are always under water:
- Box coolers and sea chests: continuously in contact with outside water, hard to inspect between dockings, and fouling directly reduces heat transfer.
- Piping and strainers: fully wetted, dark, no splash zone.
- Commercial hulls: SMART FLOW is often combined with a hard coating; the target is biofilm and mussel growth, not waterline weed.
SMART FLOW is preventive. Start with a clean surface: the system cannot remove existing fouling, it can only slow the process.
| Source | Set-up | Slime / algae | Hard fouling |
|---|---|---|---|
| Endures RPT19027 (HISWA project, 2019 season) | Two Beneteau yachts in salt water: one with two Sonihull transducers (supplied via Lamers System Care), one with one Shipsonic transducer | Neither prevented algal and slime fouling at the waterline; thin hydroid colonies by season end | Sonihull slightly better, with less barnacle fouling; “against other types of marine fouling the systems do work” |
| Practical Boat Owner (Hamble, 2014 season) | GRP cruisers with the same antifouling paint; Sonihull, UltraSystem, Citadel and SonicShield versus two control boats | No boat completely clean; lighter, easier-to-remove slime on ultrasonic boats; green weed at the waterline on all boats | No barnacle or shell growth on any hull, protected or not; some on propellers |
| Nordkyn Design (owner-built system, aluminium yacht) | Twin transducers; firmware changed for higher power and frequency | Waterline slime/algae “a known limitation”; thinner weed below the waterline after changes | Hard growth eliminated at low power |
| Port Royal Group (2024 opinion) | Review of a Florida Institute of Technology study cited by a maker | Study did not support claims for slime, algae or grass | Barnacles discouraged on about 70–85 % of the surface |
| Cathelco buyer’s guide (ESVA) | Vendor guide | Preventive only; does not remove existing fouling | Hull must be cleaned first |
Frequently asked questions
Can ultrasound replace waterline cleaning on a yacht?
The tests above say no: waterline weed appeared on every boat. If an algae-free boot-top is your priority, plan for a coating and regular cleaning.
Then why do commercial operators fit ultrasound to box coolers?
Because the cooler is a different surface: metal, permanently submerged, no sunlit splash zone, and the cost of fouling is lost cooling capacity. That is the application Lamers System Care builds SMART FLOW for.
Does SMART FLOW remove slime that is already there?
No. SMART FLOW prevents new attachment; existing fouling must be cleaned off before or shortly after installation.
Contact
Call +31 (0) 413 275 647 or email info@lscare.nl. See box-cooler antifouling and how SMART FLOW works.
