Black sand is WAY worse to keep clean looking. It's like a car, black is the worst colour to keep clean, every little speck of dirt sticks out like a lighthouse beacon.

When it's clean though it does look sharp. I have black fluorite in my FW tank and I like the look. Tough choice, I almost went and bought some myself for my new FOWLR tank but think I've let myself be talked out of it for the time being (have heard a few stories about sand sticking to pump impellers because it has metallic content).

As for particle size I find sugar sand gets hard to stay in one spot once we start getting into higher flow .. I like the 0.3 to 1.0 mm sand I'm using now (mix of Caribsea Fiji Pink and Seachem) but it's far too easily shifted around by the flow patterns, I almost wish I went with something larger even.

I don't need any denitrification function out of my sand bed.. I just want it to cover up the bottom silicone seams.