Knobber,
As you said above, snow fence is cheap. If you end up pulling with a vehicle, you might have enough force to tear a few strands of fence.
If you haven't built the full-scale algae seine yet, perhaps consider a double-layer of snow fence? That way when the first layer tries to stretch and tear, the second layer should help spread the force a little bit.
Filamentous algae delenda est!
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