Walstad method

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[edit] What is the Walstad Method?

5 Litre Walstad tank set up in one day with fish
5 Litre Walstad tank set up in one day with fish

This method of setting up an aquarium tank was made popular by Diana Walstad, author of the book 'ECOLOGY of the PLANTED AQUARIUM - A Practical Manual and Scientific Treatise for the Home Aquarist'.

  • Basically it's a tank with a natural soil and gravel substrate.


[edit] Alternative names

El Natural, NPT (Natural Planted Tank), Walstad Tank.


[edit] Principles

Provide an ecosystem where plants and fish balance each other's needs. This is typical done by providing a natural soil for the plants to live in.


[edit] Aims

  • A planted aquarium that grows plants well.
  • No injected CO2 required.
  • No or little algae.
  • No extra fertilisers added.
  • No need to vaccum the substrate.
  • No need to do any water changes for 6 months.
  • A smell free tank.
  • No denitification bacteria filled filter required.


[edit] Principle steps

3 Litre Walstad tank set up in one day with shrimp
3 Litre Walstad tank set up in one day with shrimp
  • 1 inch layer of generic potting soil available from any garden centre. Preferably with no peat added. Get non-sterile 'aquatic pond soil' if it's available.
  • 1 inch of medium fine gravel (not sand) for the top of the soil.
  • Mix in some coral gravel or shells with the soil if you think it has peat in it to make the water less acidic.
  • First plants that are added should be fast growing root plants or floating plants. Examples: Hygrophila corymbosa, Shinnersia riv., Rotala rotundifolia, Ludwigia repens, Limnophila sessiliflora, Hornwort, Ricca, etc.
  • Provide lighting. This should be at least 2W per US Gallon (3.8L) of fluorescent lighting over the length of the tank for a period of at least 10 hours a day. 'Cool white' tubes are usually all that is required. If you can position the tank so that it can get a supply of real sunlight for at least an hour a day then do so (ensure it doesn't overheat).
  • Optionally add a powerhead for water movement as plants and fish will enjoy the flow of water in the tank.
  • Test water every two days for pH, ammonia, nitrite and nitrate. The bacteria in the soil will adapt to a water existence over the following 6-8 weeks and the plant roots will establish themselves.
  • If there are signs of algae, reduce lighting time slightly.
  • After 6 weeks and the ammonia and nitrite is at zero, do a 50% water change.
  • You can add a 2 or 3 aquatic animals (though often much sooner if ammonia and nitrite is zero).


[edit] Result

  • The bacteria and plant roots in the soil will convert all ammonia into nitrate.
  • The plants will consume the nitrate.
  • The soil will release CO2 into the water and the plants will consume this.
  • Fish waste (Mulm) and uneaten fish food will be converted by the bacteria on the gravel into its component chemical parts and this will be consumed by the plants.
  • Chemicals in the soil should last the plants around ten years as the fish food will top up the chemicals the plants require.


[edit] Fine-Tuning

  • All you need do is ensure you trim the plants back as required and adjust the amount of light on the tank for fine tuning. More light, more plant growth, less algae.
  • Consider adding small snails as these speed up the mulm breakdown.
  • You'll need a water hardness (GH) of greater than 7d. Adding Sodium carbonate, coral gravel or clean sea shells will raise GH.
  • Ensure KH is never less than 6°d as you may get pH shifts at night which can harm your fish. See Sodium bicarbonate for details.
  • Add slower growing plants like Hydrocotyle verticillata and Anubias once the fast plants are established.
  • Try not to add too many aquatic animals. Test your nitrate levels monthly (or sooner after adding fish) to ensure that nitrate levels are not rising too high (ie > 10mg/l).
  • Replace the lighting tubes every 9-12 months.


[edit] Challenges

  • Some people have difficulty rooting plants once water has been added to the tank, or after pruning. The challenge here is to keep the gravel on top of the soil, without releasing soil into the water.
  • Avoid disturbing the gravel at all costs.
  • Do not use the Walstad method if you want a heavy fish load, or even a medium fish load. Light fish load only! Think a third of a normal recommended aquarium load.


[edit] Links

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