Hi there! I just realized that I can buy a 25lb bag of Mazuri rat food at Murdoch's for $23 which sure beats the price of Oxbow from Petsmart. Is this an okay switch? And is the "Mazuri Rodent" rat and mouse food the correct type for me to buy? If I switch can I just start giving them the new food or do I have to slowly switch them by mixing the old and new foods together?