Phosphorus is a mineral that occurs naturally in fruits, vegetables, and insects so it's most likely already included in your beardies normal diet. What makes this mineral important is its influence on calcium, bone development, and skeletal health.
Phosphorus and Calcium
When consumed, phosphorus will bind to undigested calcium making the calcium unavailable for absorption. This means as levels of phosphorus increase, levels of calcium will decrease.
Diets high in phosphorus but low in calcium can create a calcium deficiency in bearded dragons. The perfect ratio of calcium to phosphorus (Ca:P) is 2:1, or 2mg of calcium for every 1mg of phosphorus consumed. Diets with this 2:1 ratio will provide a surplus of calcium and allow both minerals to be absorbed.