A bioactive vivarium is only bioactive if something is eating the waste. The cleanup crew is the part of the system you rarely see and cannot skip.
Springtails
Springtails are tiny, wingless arthropods. The temperate springtail (Folsomia candida) is the standard starter: it breeds quickly, eats mold and fungus, and tolerates high humidity.
- Start with: one culture, or about 30–50 individuals in a 45 cm tank.
- Habitat: damp substrate and leaf litter; they need consistent moisture.
- Food: mold, fungus, fine detritus, decaying plant matter.
- Weakness: they crash if the substrate dries out or the mold disappears completely.
Springtails are your early-warning system. If they are crawling up the glass, the substrate may be too wet or too dry; if they are gone, something changed.
Isopods
Isopods are larger and slower. They eat leaf litter, decaying wood, and some mold. Common choices:
- Dwarf white (Trichorhina tomentosa): small, fast-breeding, good in humid tanks.
- Oreo crumble (Porcellionides pruinosus): hardy, handles a range of humidity.
- Zebra (Armadillidium maculatum): slower to establish, but a beautiful display species.
- Giant canyon (Porcellio dilatatus): larger; better in a bigger enclosure.
- Start with: 10–20 isopods in a 45 cm tank.
- Habitat: leaf litter, cork bark, and a moisture gradient. They need a dry-ish corner and a damp corner.
- Food: dead leaves, wood, decaying plant matter; a calcium source such as cuttlebone.
How many is too many?
A cleanup crew should be invisible most of the time. If isopods are swarming every piece of food, the tank is being fed too much. If springtails are coating the glass, the tank is too wet or there is a mold bloom.
Do not add a predator to control the cleanup crew. Reduce food, adjust moisture, and let the population settle.
Keeping them alive
- Add leaf litter before you add animals. A sterile tank with no leaf litter starves the crew.
- Keep a moisture gradient. Damp one side, let the other side dry slightly. Both springtails and isopods use the gradient.
- Do not let the substrate dry out completely. Springtails are the first to disappear.
- Avoid pesticides and fertilizer. Both can wipe out the crew.
- Add calcium for isopods. Cuttlebone, eggshell, or a mineral supplement.
When the crew crashes
A crash usually has a cause: a dry substrate, a mold spike, a heat wave, or a pesticide. Fix the cause before adding more animals. If the substrate is waterlogged, increase drainage and ventilation; if it is dry, mist more and cover part of the top.
A cleanup crew is not a filter. It recycles waste, but it does not remove nutrients. The plants, the drainage layer, and your water changes do the rest.
A simple starter mix
For a 45 × 45 × 60 cm rainforest vivarium:
- One culture of temperate springtails
- 10–20 dwarf white or Oreo crumble isopods
- 1–2 cm of leaf litter
- A piece of cork bark and a cuttlebone
Add them after the plants have settled and the humidity has been stable for a week. Then leave them alone. The crew does the rest.