Substrate Help

First, thanks to those who helped me out on my previous questions . Being that I'm considering some cories for the tank, I was wondering what your feelings were on substrate. I am not using live plants so I was going to use gravel for the bottom. But I'm afraid that it may damage their barbs. I know sand may be an option, but I don't have enough experience with this to worry about harming the filter and the gases under the sand. What do you think of this.....http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+10741+12134&pcatid=12134
It seems to have more rounded corners, but the size is hard to tell from the pictures. Thanks in advance.

Tahitian Moon or Eco-Complete?

OK, following up on my previous post, and what seems like a million researched threads on sand substrates, I have tried to find the Estes sand that I have seen written about. I cannot find it anywhere locally nor a search online. One LFS owner told me they dicontinued it. He recommended Eco complete, but I am not doing any live plants, and he said it may alter my pH and hardness, which I do not want to do. I want to have cories and a plec eventually. I like the tahitian moon sand. Is that a good alternative for the non planted tank and similar to the Estes?