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Veterinary, Medicine, and Health

Calcium Substrate Considerations

by Michelle M. Hewitt

About 6 months ago, I finally decided to place my desert lizards, which consist of a chuckwalla, 2 bearded dragons, and a uromastyx on the Fre-Flow. Initially, I liked it. My lizards have always been messy eaters and dragged their food onto their substrate before eating it. Feeding them outside their cages has never really worked for the chuckwalla or uromastyx. The beardeds never cared where they ate, but I did not believe the substrate would create a problem.

After about 3 months on the Fre-Flo, I noticed that the lizards were looking pale. The chalky white calcium was coating their scales. Washing did not remove the chalk for long. They were always burrowing into it I just lived with dusty looking lizards. I even started convincing other people to use this substrate for their lizards. It seemed to be a good solution. It did not harbor molds and was easy to spot clean. The animals loved to burrow. It was a great solution to the long-standing debate of substrate choices. I was not going to put everything on it but it worked for these guys.

Then, 2 weeks ago, I found my 5-year-old uromastyx dead. He showed no signs of any health problems. He was alert, active, and eating the day before. I had been taking him outside for regular sunning most of the summer and he had never looked healthier. It was a shock to us. I did not know what had gone wrong. We had this happen with a previous animal. He had died due to impaction on his substrate. That was the last time I used orchid bark. I thought this could be a similar situation. Also, my female bearded dragon started dropping weight and discontinued eating. Two animals that were doing fine, suddenly having health problems made me worry. I then started looking at the last change we made, and that was the substrate. Even before really investigating the issue, I pulled all of my desert lizards off of the Fre-Flow.

On a whim, I put some of the Fre-Flow into a glass and tried to dissolve it. Very little dissolved even overnight. I contacted Janell Osborne about the situation to hear what she knew about this substrate. She said that she knew a breeder of bearded dragons that kept his hatchlings on it but discontinued using it because he was noticing impactions in the baby's cloacas. Well, those were babies. Yet, I started investigating my adults and found pieces of Fre-Flow in their cloacas as well. I soaked my adults and started feeding them castor oil, knowing full well that the water was not dissolving the calcium, but at least stimulating them to defecate.

This prompted me to continue my investigation of this substrate. I took samples of Fre-Flow and Cal-Strate to work. I took 1g samples of each and placed them in varying concentrations of base and acid. I wanted to know if this stuff would dissolve in anything. I understand that a reptile's ability to digest food depends on many factors including temperature, but this test was just designed to give me an idea of what would happen. A lizard's stomach is an acid about pH 3 at a high concentration. Their intestines are basic at a high concentration about pH 9. In the lab I used 1M and 2M Hydrochloric Acid pH 14, tap and deionized water, and 1M and 2M Sodium Hydroxide pH 1. I added 1g of substrate to 10 mls solution. The samples were then set in a 70°F constant temperature room for 4 days. I then carefully removed the liquid and dried it. I recorded the weight of the remaining material (what had been dissolved in the solution). This is a table of my findings [below]:

Table 1 -- Results
Sample brand	Concentration	pH	% absorbed
Calstrate	2 M HCl	1	17.47%
Free-Flo	2 M HCl	1	19.31%
Calstrate	1 M HCl	1	12.29%
Free-Flo	1 M HCl	1	18.79%
Calstrate	Tap water	7	3.28%
Free-Flo	Tap water	7	2.29%
Calstrate	Deionized water	7	3.14%
Free-Flo	Deionized water	7	2.92%
Calstrate	1 M NaOH	14	14.65%
Free-Flo	1 M NaOH	14	12.71%
Calstrate	2 M NaOH	14	36.22%

Overall, this shows that the calcium carbonate substrates do not dissolve very well in any of the solutions that I made. The best I got was 36% with the 2M basic solution. Still, that is only 1/3rd of what actually has been ingested by the animal that is easily able to pass through the system. For me, that was not good enough. These particles are about 2X larger than normal sand, which has also been known to cause impactions under certain conditions.

When I continued my investigation a little further to see if anyone else had encountered problems with these substrates, I found that most breeders do not use these materials. According to Jason Creager, a uromastyx breeder, "Calcium sand acts as an antacid which neutralizes stomach acids, adversely effecting digestion."

I am not saying this material is bad under all circumstances. It still has many advantages. I am writing this so people are warned. There is a long-standing debate about sand impactions, and whether they really do cause death in desert lizards. I actually successfully raised a hatchling bearded dragon on sand, which is supposed be bad for them. One should just use caution and once again make sure that substrate is not eaten by your animals.