Hey CalGecko,
I used to keep my leos on calci-sand as well. I had a scare a little while back with one of my 3 yr old females. Whether it was impaction or not I don't know but I took her to the vet(her abdomen was very swollen, but she wasn't gravid) and she pooped a big one when they tried to get a second x-ray, so it was money well spent! Anyway, I talked to my friend Marcia at GoldenGateGeckos about my problem and she offered some very knowledgable insight on the subject. I am going to paste that part of the email in this post I hope it helps with your decision. Oh and I might add my leos are on slate tile from Lowe's now. Looks realistic and very easy to clean up, since leos only relieve themselves in one area in a cage.
Here is that email:
Hi Tim,
I'm glad you are getting rid of the Calci-Sand! I do not recommend it not only for it's potential for impaction, but for an additional reason, too. As you may know, I was a Chemical Engineer for 26 years before I became disabled... but I still dabble. Here's my theory: Calci-Sand is made of calcium carbonate, which is the main ingredient in many antacids such as Tums or Rolaids which are designed to neutralize digestive acids. Leopard Geckos have relatively short and unsophisticated GI systems, and having a constant level of calcium carbonate in their intestines not only can cause blockage or impaction, but also reduces the digestive acids and enzymes necessary for proper digestion. I know of a few lab experiments that were published on the solubility of Calci-Sand in water, and it was proven it does not dissolve as well as the manufacturers claim it does.
Hope this helps
Tim
-----
LEOs: 3.11.0
1.3 High Yellows (Barney and Betty);1.3 Hypo Tangerines(Bam-bam and Pebbles); 1.1 Rescued Normals (Shleprock) 0.4Tremper Albinos (No names yet), Lookin for a good male Albino breeder
BEARDIES 1.0.0
Snow and Yellow (Fred)