Vitamin D3 and Phosphorus are vital in maintaining good health of your amphibians. However, as with all things, too much is just as bad as too little. The amount of supplements to use will vary with species. I suggest serving dusted food items no more than 3 times a week. This is the protocol I used at the zoo when I cared for many different species. Vitamin D3 can also be obtained through UV-B lighting.

I also suggest the administration of one drop of liquid Vitamin A on their backs once a week. This will prevent feeding problems.

Articles of interest:
http://www.amphibianark.org/pdf/Husb...tamin%20D3.pdf
http://www.amphibianark.org/pdf/Husb...0nutrition.pdf
Do Your Frogs or Toads Have Trouble Catching Insects?