Two technologies compete for the “best non-paint anti-fouling” title in aquaculture: copper-alloy net mesh and silicone foul-release coatings. Both avoid the environmental problems of copper-based paints, but they work in completely different ways and suit different farm setups. See the full anti-fouling methods comparison for side-by-side ratings.
Copper-alloy nets are made from copper-nickel or copper-zinc alloy wire instead of nylon. The copper surface is inherently toxic to fouling larvae — organisms simply cannot attach and survive. Field trials consistently show 90-95% fouling reduction compared to uncoated nylon. The nets also last longer physically (5-7 years vs 2-3 for nylon) and are predator-resistant. The downside is cost: copper nets run 3-5 times the price of nylon, and they are heavier, requiring stronger mooring systems.
Silicone foul-release coatings take the opposite approach. Instead of killing fouling organisms, they create an ultra-smooth, low-energy surface that organisms cannot grip. Fouling attaches weakly and detaches under water flow or light mechanical cleaning. Early trials (Hodson, Lewis, and Burke, Aquaculture, 2000) showed 60-80% fouling reduction. Modern formulations perform better, but they need water movement to self-clean — sheltered sites with weak currents still accumulate fouling on coated nets.
The practical trade-offs: copper nets are closest to a “fit and forget” solution — minimal cleaning needed for 5+ years. But the capital outlay is substantial, and copper does leach into the water (at lower rates than copper paint, but still measurable). Silicone coatings are cheaper to apply but need recoating every 2-3 production cycles, and physical damage from handling or cleaning breaks the surface.
Where each wins: copper nets are best for high-fouling sites (warm Mediterranean waters, sheltered fjords) where cleaning costs are extreme. Silicone coatings suit farms with moderate fouling and good water flow, where the self-cleaning effect keeps surfaces manageable between lighter mechanical cleans.
Most farms weighing this decision end up asking a simpler question: how bad is our fouling? If the answer is “nets are fully encrusted within two months,” copper alloy is probably worth the premium. If it is “manageable with regular cleaning,” silicone can reduce that cleaning workload at lower cost. The biofouling cost calculator can help you model both scenarios. For background on regulatory trends affecting copper-based products, see our dedicated article.