Thinking about going bioactive

[akane]

You can go the expensive route or just go somewhere you know hasn't been sprayed with chemicals, dig a hole, discard the top plant matter and any bulbs or major roots that could regrow, mix the resulting soil, critters, and probably a few roots with enough sand or clay to "taste" for your setup. Sometimes you want something that drains more and sometimes you want something that holds more. Sometimes some larger particles like small gravel (natural colored aquarium versions work well), crushed coral, crushed lava rock, etc... can help provide more structure so it doesn't compact but my desert tank for my rosy boa is mostly white quartz sand (~60%) with coconut compost. Various composts and organic materials can be used for increased nutrients for plants and for critters. Plus compost is usually fairly loose material so it helps avoid compacting on it's own and by having things wander around eating it. Various dried leaves, often partially crushed and sometimes collected off the ground wet to gain more critters, is usually added to at least part of the tank for critter food and more organic matter. You may get mold or fungus depending what you use and how wet your setup needs to be kept for its inhabitants but the soil critters will take care of those eventually.

The drainage layer may or may not be necessary and may be simple or complex. In my desert tank it is not necessary. There is not enough moisture collecting to have standing water and it drains rapidly away from the top. Low humidity tanks take special care to setup areas for your isopods and soil critters that stay moist and have organic material. Light, soft wood works great. In my bullsnake enclosure I made a very deep, heavy substrate of mostly yard soil and coconut compost with several inches of playsand under that so I just stuck a layer of river rock in there with no divider. In my smaller Dekayi enclosure I found my soil fell through my thinner drainage layer filling in the lava rock on the bottom and I could not get the thing dry in our humidity. I redid it with plastic craft mesh as a divider and some sand with the rock to help allow the water to drain out and the soil to stay separate. The soil layer is also much thicker partially planned and partially I just didn't realize how much was living in his previous enclosure so I ended up wanting to use it all. You can see it in my Dekayi thread in the general colubrid section. I took one pic with flash so the divider and rock would show up at the bottom.

I've got all sorts of centipeds and milipedes, some regular worms, some white thin worm things, some isopods, I think the springtails were killed by predatory mites but normally springtails would take over with plenty of leaf litter or organics to eat, of course as said I have various soil mites... Sometimes it's fun to just look at the critters after dark with a flashlight and see what's come out to move around on top or loosening up the soil from the middle.

It's as easy or complicated and as cheap or expensive as you want to make it depending how creative you get with materials and the drainage design you follow. Plus what your inhabitants are going to do to it. Some burrow extensively and others don't. I set the bullsnake in thinking he'll find a rock hole to hide in and nope he slipped right down in the soil and all you saw was this little trail of disturbed surface soil disappearing under the rocks and wood. I was warned my layering might just become a mix eventually. I placed base rock like you do in saltwater tanks with deep sand beds so that the animals can't dig under the surface rocks and crush themselves. Then you put your decorative rock on top of the cheap base rock at the top of the substrate layer.