With the mesh cage, get a deck scrubbing brush and scrub the mesh on the sides of the cage. That will remove any FA that forms.

I have plastic cage netting that has held up for 10+ years without any degradation from the sun. You can get it here:

https://www.industrialnetting.com/cage-netting.html

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).