I just bought my first dragon 3 days ago and I bought him the calcium sand. The guy at PetSmart seemed to think that it was ok (and he was veryknowledgable about beardi's) but people are saying on here that it is not good for them. What about he sand is not good for them, what will it do?

Also from what I have learned so far beardies are ok to not hav a heat source at night as long as the temp doesn't drop below 65 is that correct? My tank stays about 70 at night. I am new at this so any tips are appreciated!