Beach High Banker, Sweep Jig, Whippet Dry Washer, Lobo ST, 1/2 width 2 tray Gold Cube, numerous pans, rocker box, and home made fluid bed and stream sluices.
OK, I will give it a quick shot. The answers above are good as far as they go. The Bazooka is the best commercial fluid bed sluice out there today that I know about. It uses a long slick plate to let the dirt, rock, gold, sand, black sand start to stratify. The entire shovelful of material goes over a grizzly that allows material less than 3/8" to drop in the fluid bed area. The oversize is washed off.
Inside the bed, the fluidization allows the lighter material to "float" to the top of the bed the heaver material to sink. As the bed fills up, the light material on top of the bed is eventually pushed out as more and more heavier material goes to the bottom of the bed. Thus gold and black sand are "trapped" and the light material is washed out. The bottom of the sluice as you look at the slick plate has a section feeding water continually to the fluid bed to allow this to happen. There are no riffles, no mats, no carpets.
The Bazooka catches fine gold very well; we are talking up to 100 mesh extremely well. DIY fluid bed designs are posted here at Treasure Net and other places.
Beach High Banker, Sweep Jig, Whippet Dry Washer, Lobo ST, 1/2 width 2 tray Gold Cube, numerous pans, rocker box, and home made fluid bed and stream sluices.
Maybe more simply, the actual "fluid bed" is the box without a top (the "bed") and water circulates through the material in the box keeping it "fluid" so heavy stuff sinks right to the bottom.
Here's mine. Just a box with a lot of spraybars to keep the material suspended. In use, each bar creates a zone of boiling similar to a spring. Works real well with Lake Superior beach sand. I run as a recirc to avoid MI pump permit requirements. I'm working on a header box for it so I can just shovel into it without classifying.