Regime
Walstad
Philosophy
The Walstad method, established by microbiologist Diana Walstad, is the definitive approach to ecological and natural aquarism (Natural Planted Tank). The guiding philosophy is to create a self-sustaining ecosystem where biological balance is maintained through natural interactions among plants, fish, and soil microbes, minimizing human technological and chemical intervention.
The core of the system is a substrate consisting of ordinary, untreated organic potting soil capped with inert gravel. The soil acts as a vast reservoir of nutrients and, crucially, carbon dioxide (CO2) generated by soil bacteria decomposing organic matter. Plants absorb nutrients primarily through their roots, while their leaves process the CO2 and release oxygen to keep the substrate healthy. Fish waste and food provide all the required nitrogen, phosphorus, and potassium, eliminating the need for liquid column dosing. Plants serve as the primary biological filter by directly absorbing ammonium (their preferred nitrogen source) and heavy metals, minimizing the need for traditional filtration and frequent water changes.
Recommended nutrient targets
| Parameter | mg/L |
|---|---|
| N (NO₃) | 3 |
| P (PO₄) | 0.3 |
| K | 5 |
| Fe | 0.05 |
| Mg | 2 |
| Ca | 15 |
| B | 0.005 |
| Mn | 0.02 |
| Zn | 0.005 |
| Cu | 0.001 |
| Mo | 0.001 |
Dosing frequency
Minimal or none (substrate and bioload provide nutrients)
Water change
10-15% every 2-4 weeks
CO2
Not necessary
Light
Moderate (natural light or moderate LED, 6-8h)
Pros
- Minimal maintenance
- Ecologically sustainable
- Affordable
- Self-sustaining ecosystem
Cons
- Complex initial setup (soil)
- Less controlled aesthetics
- Difficult with demanding plants
- Risk of initial cloudiness
Common Errors
- •Using potting soil with added chemical fertilizers (causes chemical disasters).
- •Stocking too few fish or plants: the system relies on the ecosystem, needing a healthy biological load and a jungle of plants.
Advanced Techniques
- •Adding a tiny layer of pure laterite under the soil to ensure a decades-long iron reservoir for deep roots.
Ideal for
Those seeking a natural, low-maintenance aquarium with hardy plants and a balanced ecosystem.
