Neon tetras won't last very long with Oscars. Funnily enough, I am putting black sand in my new 300 gallon tank, it should look stunning. To answer your question, it will certainly show off the fish well, especially if they are silvery fish. I have got some really nice pebbles to go on the sand, I'm hoping to get some really big ones as well. I've got some fake Amazon swords which I will have coming up between, hopefully they will work okay. I've also got to really big bits of wood, quite looking forward to getting it set up