Spring Tails are tiny hexapods averaging around 0.5 mm in length. These little guys will live in the topmost layer of your bioactive substrate and consume any waste that they come across. When they themselves have taken what they need from this food source they excrete the excess nutrients which goes back into the soil to be used by any live plants you might have in the enclosure. They are very efficient and once a colony is established should work fairly quickly to keep the cycle moving. There are foods available you can add to your substrate for the spring tails but usually they are pretty self-sufficient.