crushed coral

Hello everyone, I’m setting up a new bigger tank for Squirt since he’s just a little over 3 inches now. Since he’s getting bigger I’m getting worried about him because he’s grazing on the bottom of the tank with the gravel rocks. So since I’m doing a whole new and bigger tank setup I thought this would be a perfect time to replace the substrate in the bottom of the tank. I would like to go with crushed coral since it seems to be the best, but I don’t know much about it. From looking up info on it on dbt world, it seems that jonathon recommends #5 but I haven’t had much luck finding number #5 and I do not know exactly what #5 means, I assume it refers to the coral size. So I was wondering if anyone knew of any links or if the coral sold through Big Al’s would be fine. The coral sold through Big Al’s is on this webpage: http://www.bigalsonline.com/catalog/product.xml? product_id=33906;category_id=2409 Thanks Walls I appreciate the knowledge this group shares and spreads.