If you want clean and black then either paint it or use absolute black granite tile. I had it in my tank for about a year before the tank leaked. The tile is flat on the back and the edges are square so nothing get in between them. If you use ceramic tile you really need to silicone the bottoms of them but you can't do that with water in it. I avoid black worms at all cost because they are so messy. Nothing like cleaning a canister and finding it full of the nasty little things LOL
I used Estes sand in my 72 bowfront when I first got my motoros. They were small and I wanted to put some weight on them. The sand was so fine that is was continuously getting kicked up and sucked in my sump and hang on the back filter. It was a pain and I had to continuously clean out the sand. Before I moved them to my 210, I wanted something heavier and I don't like the look of bare bottom tanks. I ended up getting 8 (20 pound) bags of caribsea instant aquarium torpedo beach sand. The grain size is quite a bit bigger and settles quickly when disturbed. I don't have any issues with the stuff ending up in my overflows or sump. Fish waste doesn't go through it either. When the rays swim over the sand it kicks up the waste and it gets filtered out. So i don't need to siphon the sand. I tried once but no detritus came through.Tank looks great and it's never cloudy. It is ray safe as well. I got it at petsolutions.com and paid $19.99 for each 20 pound bag. Shipping is free if you spend over $49.
thank you for all the feedback everybody and sorry for the delayed responce, crazy week. The bare bottom is growing on my simply because it is SOOO easy to keep clean. In the near future I will be adding sand but for now, boring bare bottom for me!