Nope. If you load the viv up with microfauna (springtails and isopods), you shouldn't need to replace the substrate for a few years.
probably an even stupider question..... What IS an isopod? can I buy them at my grocery store and replant them or do I hve to buy them rom a herp store and plant th as seeds? I'm sorry I'm new to this. fortunately I don't havea frog yet lol.