if you buy Aristopet Repti-cal , note it contains large sharp shards of insufficiently ground oyster shell (my observation over the last 2 years is this can be as much as 20 -30% of the mass of calcium in the bottle - NOT GOOD ENOUGH !!! ) they claim it's safe for your pet to ingest these large sharp particles of oyster shell , you'll need a flour sieve to separate these nasties from the fine Ca powder. (which should be under 250micrometer in particle size , they apparently changed their process resulting in these large particles no longer being removed in their screening process (last year)).
Phosporus interfers with calcium metabolisation , so NO Phosporus.