What is bioactive substrate?, It’s basically a substrate that contains bugs that eats the poop and food leftovers from your animals, and to be really bioactive it has to contain plants and the microbes that can breake it into nutrients for the plants. Its not difficult to set up, and has been used for many years by frog keepers. What has worked well for me is to use a loose substrate that can is a good substrate for the iguanas to lay eggs in and at the same time is a good substrate for the bugs to live in. As for the substrate itself, i normally use forest floor from our local little beech tree forest. It often contains alot of different bug species besides the springtails and woodlice. Other bugs often found is milipedes and our native centepedes ( they are too small to pose a threat to the iguanas), and sometimes there will also be a few slugs, but they dont seem to thrive inside the iguana cages. The forest floor itself is rather loose, and is a mix of decaying leaves and branches, a bit of soil and small stones. Of bugs commenly used, there are springtails and woodlice. Springtails are easiest to just buy as it can be difficult to find enough outside to make a sustainable culture inside the cage. Woodlice can be much easier to find outside. they can often be found under rotten tree or stones. I have tried alot of different plants in my cages and the once that have done best has been pothos. Photos is saind to be toxic, but to my knowledge pothos dont contain any toxins, but it does contain oxalate crystals, that to some animals can irritate the mouth if eaten, but i have not witnessed that with fijian iguanas even they do enjoy eating the young leaves from time to time.