Miners moss is great as Gav pointed out it has a large surface area. Its great as acting as a fluid bed. Its disadvantage is it can pack up with heavies especially in high iron sand areas if you have interruption to your flow. This is probably more relevant in a dredge or HB situation where you might turn your dredge off or on multiple times. In a stream sluice it’s obviously different.
Tbe Keene Green carpet is pretty good on fine gold under raised expanded however as Dave Mccrakens says the best medium for fine gold is raised expanded over deep V matting. He also reakons ribbed or Keene green carpet is excellent as well.
The disadvantage with carpet is that it tends to hold oily products ie fat and oil from your hands and the environment alot more effectively than miners moss. This can result if the carpet is not washed in fine gold loss.
That’s why you should be clean your whole sluice every month or so with warm soapy water.
There’s many schools of thought with many opinions on tbe miners moss vs carpet debate. .
The miners moss sold in Proline dredges which has a weave thats thinner than most of tbe miners moss I’ve seen. I think its 3M product is excellent.
I think the key to any recovery is not exactly what mat your running in your sluice but more things like water flow and classification. Classification is one of the best things you can do for recovery especially in fine gold areas.