Stop the moss growing on stainless water flume

We have had stainless steel panels punched with rows of .093 holes for a water flume, to allow fish to pass unharmed and separate the water for use. The problem is moss is growing on the underside, We think from the very small burr left from the punch. We had the burr electropolished off in an effort to not give the moss a place to get a hold of. The surface is now very bright and the moss growing faster than ever. Is it not true that E Polishing is to leave a more bacteria resistant and clear surface? Does the bright surface have something to with it?

For moss, the first thing I would try is placing a zinc sheet ⇦ on eBay or Amazon [affil link] or bar just upstream the stainless. Zinc is used often on roofs to control moss.

The electropolish should leave a surface with less large scale surface roughness, but it may still leave a lot of microscopic scratches--moss doesn't need much.

I suspect that the reflectivity is helping a little, but more likely the surface is now smooth enough that the moss has no competition.

Talk to your state biologists about the moss control issue--and to verify that whatever steps you take are safe for the fish and other uses of the water.