I have tried everything with sustrate and like Tahitian Mood Sand Black the best, but it darkens my fish so much I can't see them, so I'm going with natural, light sand. If you use sand, gases can trap under it, so stir it up a bit and it's easy to see the poodoo and suck it up.
You loose a little sand during waater changes, but it's worth it. Rinse and soak it well first, break up all the little balls. I keep sand at about 1/2" max