Dougall is right, Sprinkle. A little patience. It's hard, I know, shoots, even I want to jump the gun sometimes. But think of your tanks as a fine wine. It's not so good at first but it improves with age.
After having the same experiences as you with soil and a gravel cap the first few times, I started using sand to cap the soil in my Walstad-style tanks. I have also always used a small filter, which wasn't part of her original process if I remember correctly, and I've also was never able to use natural light because of the placement of tanks. I've also cycled the tanks normally before adding anything living, plant or animal. Of course, this was before the internet was well-established (maybe it didn't even exist, for all I remember) and I didn't even think about forums. I wish I would have had an internet the first few years of my hobby experience.
When freshyfresh talked about the gravel sinking to the bottom, well, that is something that will happen over time, not something that will happen immediately. It does look like it may start to sink eventually, especially when you start adding plants. IME it's almost impossible to not have a bit of the dirt released into the tank when planting anyways, regardless of the cap medium, so make sure the soil is inert without any additives or man-made substances.
So this is what I would do. I'd siphon out the particles and empty the tank of water completely. I'd then either carefully scoop out the cap layer and replace it with a finer gravel or sand,
or I'd scoop out half the cap layer of gravel and replace it with sand while carefully mixing the sand and the remaining gravel into a single homogenous layer. I'd then carefully add water and start cycling the tank. When adding water, place a small bowl or dinner plate in the tank first and pour or run the water into the bowl/over the plate. This will help reduce the substrate being stirred up and destroying the integrity of the cap layer, thereby reducing how much soil gets stirred up. Just move the bowl a bit every now and then so that the water overflowing the sides doesn't move the cap layer so much that it gets down to the soil layer.
WYite