A planted 10 gallon using the Walstad method is a self-sustaining ecosystem — soil feeds the plants, plants filter the water, and you do minimal maintenance. No CO2, no fertilisers, no expensive equipment. Here's how to build one that actually works, using the Walstad Soil Calculator to get the substrate right.
What is the Walstad method?
Diana Walstad's approach uses organic potting soil under a sand cap as the substrate, with heavy planting and minimal filtration. The soil provides nutrients to the plants for years; the plants process fish waste. Done right, a 10 gallon Walstad tank can run for months with only occasional top-ups and 20% water changes every 2 weeks.
Substrate layers
Use the Walstad Soil Calculator to calculate exact volumes. For a 10 gallon:
- Organic potting soil: ~1.5–2 litres (2.5–4 cm deep). Must be organic — no perlite, no fertiliser pellets, no moisture crystals.
- Sand cap: ~2 litres (2 cm deep). Play sand or pool filter sand. This seals the soil and prevents it leaching into the water.
Best plants for a 10 gallon Walstad
Plant heavily from day one — 70%+ coverage minimum. The plants need to be established before you add livestock:
- Heavy root feeders: Amazon sword, cryptocoryne, Vallisneria — these pull nutrients directly from the soil
- Stem plants: Rotala, Ludwigia, Hygrophila — fast-growing, absorb nutrients from the water column
- Floating plants: Frogbit, salvinia, duckweed — nitrate absorption and light diffusion
- Moss: Java moss, christmas moss — shrimp hiding places and biofilm surface
Livestock for a 10 gallon Walstad
After the tank has been planted and running for 2 weeks (to let the soil settle), add:
- Cherry shrimp colony (10–15) — the clean-up crew. They'll breed in this setup.
- Nerite snails (2–3) — algae control on glass and hardscape.
- Small fish (optional): 6–8 ember tetras OR 1 betta. Don't add too many — the plant filtration can only handle so much bioload.
Maintenance
One of the benefits of the Walstad method is low maintenance:
- Water changes: 20% every 2 weeks (not weekly)
- Top-ups: As needed (evaporation)
- Trimming plants: Monthly — remove excess growth
- Feeding: Very sparingly — the shrimp and snails get most of their food from the tank's biofilm
Never do a full water change — it resets the bacterial balance. If the water goes cloudy (bacterial bloom), leave it alone — it will clear in 7–10 days.
Frequently Asked Questions
Can I use dirt from my garden instead of potting soil?
You can, but I don't recommend it for your first Walstad tank. Garden soil composition is unknown — it may be too rich (ammonia spikes) or too clay-heavy (compacts and goes anaerobic). Organic potting soil is predictable. Once you've done 2-3 successful Walstad tanks, experiment with garden soil if you want.
How long until I can add fish to a Walstad tank?
Wait 2 weeks after planting before adding shrimp/snails. Wait 4 weeks before adding fish. Test ammonia and nitrite — if both read zero, the tank is ready. The soil may release ammonia for the first 1-2 weeks, so don't rush it.
Do I need a filter in a Walstad tank?
Strictly speaking, no — the plants handle filtration. But I recommend a small sponge filter for water movement and oxygen exchange, especially if you keep fish. A Walstad bowl (shrimp/snails only) can run without any filter at all.