Earlier this month a listener asked me which substate was best for a certain species. I started thinking about the different substrates that I have used over the past thirty years and rather than choose one, I thought it would be interesting to discuss some of the pros and cons associated with various substrates. When choosing a proper substate it is important that we consider the animal's natural history and whether or not we are looking to go naturalistic or utilitarian. Each species has its own specific needs and sometimes even individual animals benefit from different substates at different times. In this episode I discuss everything from humble paper towels to more derived and complicated substates, and situations where they are appropriate.