I did my own rock. Made about 300lbs of it. Took me about 9 months, and that was being pretty lazy about it. LOVED IT! Had a lot of fun creating some pretty cool stuff. Crushed arragonite, #1 Portland cement, Morton's rock salt, and some creativity. I used 3 different size grades of arragonite, #15, #5, and sand grade. Even mixed some crushed clam shells and crushed lava rock into some of the mixes. Also, payed with acid buffers, vinegar baths, muriatic acid baths, even a 24hr dip in the LI Sound. Had a blast making them. Getting ready to start another batch, soon. If you decide to take on a project like this...BE PATIENT and Be diligent with your water changes. It pays off in the end.