It may take several years for a deficiency to actually make a bird clinically ill. In excessive quantities, many of these minerals can also be toxic. The key is to provide your bird a balanced diet. The rest of the calories should consist of fresh fruits and vegetables as well as an appropriate protein source. These supplements need to be prepared and cleaned up at least once daily.
Pellets require virtually no preparation time.
Can leave a healthy bird unattended for a weekend with a pelleted diet. Nutrients are calculated based on all seeds in a mixture AND their hulls. All birds will not eat the hulls of most seeds. Most birds will only eat a few varieties of seeds from the mix. Therefore, they are receiving only a few of the nutrients in an already deficient diet.