Attribution
Ranked by how much damage each one does.
One. "The Walstad method means no maintenance." Her book's section heading is "Low Maintenance", and the text under it defines the term: her tanks often go six months or more without a water change, and routine maintenance is replacing evaporated water and pruning excess growth.1 Two named ongoing tasks. In a tank growing as well as she describes, the pruning is substantial. In April 2026 she reported trimming Vallisneria heavily and pulling out excess floaters to stop them taking over.5
The phrase people are half remembering may be the title of her 2004 article, "The 'Do Nothing Club' That Does a Lot"8. Read the second half of that title. Low intervention is not no maintenance, and the difference is why beginners abandon the method at week three.
Two. "Just put any garden soil in and it works." Soil selection is a numbered subsection of her substrate chapter with its own page range, sitting alongside sections on mineralising potting soils and on soil fertilisation1. She names what she uses: Piedmont clay topsoil plus bone meal4. And in April 2026 she published a soil failure of her own, with the nutrient analysis of the bag that failed and the fix she applied.5
The truth underneath the myth is narrower and more useful. An ordinary cheap soil can work, and no branded product is required, but which ordinary cheap soil is the single most consequential decision in the whole method, and it can fail in both directions.
Three. "She proved that plants suppress algae chemically, by allelopathy." Not her current position. In the fourth edition's own chapter summary she describes herself as briefly touching on the possibility of allelopathic interactions, and the subject occupies about two pages of a chapter that runs twenty one.1 Her four part series in 1995 and 19968 was a much stronger statement, and it was written seven years before the field had a standard review9. She moved with the evidence over twenty eight years910. The hobby is still arguing with the 1996 version.
Her own six point definition1
- 01
- No artificial CO2 injection
- 02
- A substrate containing ordinary soil. She calls this one essential component
- 03
- Reliance on plants rather than filters to purify the water
- 04
- Bacteria and fish, not a cylinder, supply carbon dioxide
- 05
- Plants and soil bacteria, not biofilters and water changes, remove ammonia
- 06
- Fish food and soil, not bottled fertiliser, supply trace elements
The credential, stated precisely
Two more worth flagging
There is no 2025 or 2026 edition.
The fourth and current edition is April 2023, ISBN 979-8-9875741-0-21. The 2025 book is a different book, Aquarium Fish Reproduction, with a different ISBN.24 This error is now widespread enough to appear in retailer listings.
Two more worth flagging
"Walstad tanks never use filters."
She removed hers and reported the fish were fine2, and she runs recent tanks without filters or aerators5. But Color Plate 3 of her own book shows a tank with over a hundred juvenile cichlids running a hang-on-back filter, described as a success.1 The principle is that a filter is a rival to the plants for ammonium and a route for carbon dioxide to escape. It is not that filters are forbidden objects.
The even handed verdict
It works reliably for the thing it is for, and it is oversold for everything else.
The strongest honest criticism is not that it fails. It is that it is credited with more mechanism than it has earned. How much of its success comes from the soil specifically, as opposed to from low light, heavy planting and patience, is a live question that nobody has settled11.
| It is the right method for | Why | It is the wrong method for | Why |
|---|---|---|---|
| Longevity | She kept rainbowfish continuously from 1988 to 2017.1 A soil substrate with cation exchange capacity is a buffer, and buffers make systems slow. A high-tech tank degrades within weeks if you stop managing it | A rescapeable show tank | Every rooted plant you pull releases a cloud of soil. Her own April 2026 rebuild needed a 30 percent water change and fresh washed gravel after one afternoon's work4 |
| Cost | Soil, gravel, a light and plants, against a cylinder, regulator, solenoid, diffuser, drop checker, dosing pumps and branded soil | Demanding carpets | Hemianthus callitrichoides, Micranthemum Monte Carlo, Glossostigma, hairgrass carpets and fast red Rotala all want strong light and injected carbon. Strong light without injection is the algae trap |
| Fish health | Plants remove ammonia within hours, take up heavy metals, prevent the slow acidification nitrification causes, and oxygenate. The pH argument is checkable: nitrification generates two protons per ammonium oxidised2 | Deep tanks | Light attenuation. Her successful tanks are shallow, and she names shallow depth as one of three reasons her 2026 expo tanks needed no filter or aerator5 |
| The plants people can actually buy | Cryptocoryne, Anubias, Microsorum, Vallisneria, Echinodorus, hardy stems, mosses and floaters all do well without injection | A clean looking tank in the first eight weeks | Algae in the first two months are normal. Her stated goal is control, not eradication.1 A hobbyist expecting a shop display tears the tank down at week three |
| Small scale, and shrimp or fry tanks | High-tech methods scale badly downward because the equipment does not shrink. And no filter to suck in shrimplets, plus a biofilm rich substrate | Anyone who wants a soil they can buy | There is no bag labeled Walstad soil. The most consequential decision in the method is the one a beginner is least equipped to make |
Her own practice is more varied than the label. She runs at least three configurations: the soil underlayer display tank that people mean by a Walstad tank; nine breeding tanks for guppies with potted plants, a thin scattering of gravel, no soil layer and no filters7; and small soil bowls of about a gallon under a window1. She also publishes her failures. The one gallon shrimp bowls were fun for about eight months and then were simply too small to sustain a population, so she stopped.1 This is not promotional literature.
The genuinely useful part
In a country with no ADA distribution, this is not the budget option. It is the correct one.
The Walstad method is the only major planted tank philosophy whose core input cannot be import blocked, because the core input is dirt.
ADA, Tropica, Chihiros, Seachem, Twinstar, UNS, Aquario, Do!Aqua and 2Hr Aquarist could not be found stocked anywhere in Armenia. The entire national substrate offering at the largest specialist shop is eleven items, of which the only real aqua soil is ISTA Premium Soil at roughly 24,000 AMD for 8 liters, plus a generic aqua soil, a Dennerle quartz and an Aquaforest bio sand.20
Run the arithmetic on a 60 by 30 cm tank. A 5 cm aqua soil bed is about 9 liters, so two bags, about 48,000 AMD, before light, tank, plants or anything else. The Walstad equivalent is roughly 5.5 liters of soil and 5.5 liters of gravel.22 The soil is free or a few hundred dram. The gravel, in a country whose rivers run over volcanic rock, is close to free too.
That is not a marginal saving. It is a different price bracket, and in a market with no ADA distribution it is the difference between a planted tank existing and not existing. The method the international hobby press treats as the beginner's budget option is, here, the structurally correct one.
| Property | Yerevan value | Why it matters for this method |
|---|---|---|
| GH | 2.9 to 10.9 dGH by district1222 | Comfortably inside the range for both the soft water and the hard water plant groups |
| KH | roughly equal to GH, so about 3 to 11 dKH22 | Calculated, not measured. This is the carbon reserve. See below |
| pH | 6.0 to 7.312 | Near neutral, which is where a submerged soil converges anyway |
| Bicarbonate | 61 to 77 percent of all anions12 | Everywhere in the city. A real, usable carbon reserve for bicarbonate using plants |
| Sulfate | rarely above 11 or 12 percent of anions12 | Low sulfate means low hydrogen sulfide risk in the soil layer |
| Ammonium and nitrite | not detected anywhere12 | A clean baseline for reading your test kit during the first weeks |
| Heavy metals | Cu, Zn, Pb, Cd, Fe, As at or below detection in almost all samples12 | The tap water is not a metal source. The soil might be |
| Source geology | volcanic andesite and basalt of the Gegham range12 | Not limestone, which is why the water is soft and bicarbonate dominated |
Why the bicarbonate matters
Her most recent journal article is called "Bicarbonate as a Carbon Source".
It ran in April to June 20238, and her book has a section on bicarbonate use1. Yerevan water is 61 to 77 percent bicarbonate on the anion side12 at 3 to 11 dKH22. That is a real carbon reserve for the plants that can use it, and it is exactly the carbon route she says a low-tech tank should exploit. Vallisneria, Egeria, Elodea, Hygrophila, Ceratophyllum and Potamogeton are all good bicarbonate users. That is a specific, locally grounded reason to expect this method to work here.
Choosing soil for your tank
Do not dig soil in urban Yerevan. A 2017 assessment of heavy metals in the city's soils found lead exceeding the pollution index threshold in 99.9 percent of samples, significant mercury contamination city wide, and moderate contamination with vanadium, nickel, copper, zinc, chromium and arsenic. It identified a non-carcinogenic risk to children across the whole city.13 A 2024 follow up mapped the lead anomalies specifically and found lead traveling with copper and zinc as a persistent human signature.14 Both papers are paywalled; both abstracts state the findings.
This is not a theoretical worry for a fish tank. Walstad's entire second chapter is about heavy metals in aquariums, how they poison fish and how plants detoxify them. She made metals chapter two of ten.1 Urban Yerevan park soil is precisely what that chapter warns about.
Also avoid mining influenced regions. Lori has a documented high arsenic background compounded by historic mining.17 Shirak topsoils average 15.1 mg/kg arsenic and 12.5 mg/kg lead.18 Vanadzor has documented copper, lead, zinc and chromium anomalies14. Syunik is copper and molybdenum country.
What is likely to be good is agricultural or rural garden soil from the Ararat plain, away from Yerevan and away from the mining regions. It has two documented properties that are good news. Phosphorus is high: the first geochemical survey of phosphorus in Ararat Valley soils found 493 to 1,932 mg/kg with a mean of 891, about 1.53 times the global soil average.15 Phosphorus is the nutrient most often deficient in a soil substrate, and the one she adds bone meal to supply. Armenian soil may not need it. Micronutrients are adequate and then some: Ararat region agricultural soils run zinc 55.6 to 219 mg/kg and copper 42.1 to 189 mg/kg.16
The single most locally relevant caution on this site
That copper figure is also the warning.
Typical uncontaminated world soils sit around 20 to 30 mg/kg of copper. Ararat farmland at 42 to 189 mg/kg16 is well above that, and it is consistent with decades of copper based fungicide on vines and orchards in a copper mining country.
Copper is acutely toxic to shrimp and to snails at concentrations that do not bother fish. If you plan a Neocaridina tank on Armenian farm soil, this is a real and specific risk. Test the soak water with a copper kit, which is cheap and widely sold even where nothing else is. If no kit is available, treat farmland soil from an old vineyard or orchard as unsuitable for a shrimp tank on precautionary grounds, rather than testing it on live animals.
Terminology for the Armenian edition
Հող, not սննդահող.
Substrate is հատակաշերտ. Aqua soil is սննդահող, literally nutrient soil. Plain soil is հող.20 A Walstad tank uses հող, and that distinction is the whole point of the method.
One more naming trap. Volcanic scoria is հրաբխային խարամ. Never write just խարամ, which means furnace slag.21
| Rank | Source | Reasoning |
|---|---|---|
| Best | Subsoil clay from a building excavation or a rural hillside, away from roads, away from Yerevan, away from mining districts | Mineral, low organic, high cation exchange capacity, low contamination risk. The closest local equivalent to her Piedmont clay |
| Good | Rural agricultural topsoil from Ararat, Armavir or Aragatsotn, from land you can identify | Ideally not an old vineyard or orchard, because of the copper history |
| Acceptable with preparation | A bagged garden or vegetable soil (հող) from a garden center | Check it against the exclusion list, and mineralise it first if it is peat and bark based |
| Avoid | Yerevan park and courtyard soil, roadside soil, soil from Vanadzor, Alaverdi, Kajaran, Kapan or Agarak | And anything containing added fertiliser, perlite, manure, lime or water retaining gel |
How to test a soil before it goes in a tank
None of this needs a laboratory. Do all of it. Each test takes minutes and each catches a different failure. The five tests below are our own protocol, not a published method.
Look and crumble. Wet a handful. It should smear like plasticine, not crunch and not spring back like sponge. Bark chips, white perlite balls, fertiliser prills and fibrous peat are all reasons to reject the bag.
The jar test, for texture. Half fill a straight sided jar with soil, top up with water, add a pinch of salt, shake hard, leave 24 hours. Sand settles in a minute, silt in a few hours, clay last. You want a visible clay band, because clay is where the cation exchange capacity is. Pure sand is useless as a substrate.
The soak test, and this is the one that matters most. 200 ml of soil in a jar with 1 liter of your own tap water, in the dark, at room temperature. Test ammonia at day 2, day 7 and day 14. Still high at day 14 means too rich in nitrogen: mineralise it or reject it. Near zero at day 2 and staying there is probably fine and probably lean. A rotten egg smell rather than an earthy one means reject.
The pH check. Test the soak water against your untreated tap water. A large drop means a peat heavy acidifying mix.
The copper check, if you plan shrimp. Test the soak water with a copper kit. This is the only practical way for a hobbyist to catch the Ararat copper problem.
Provenance beats testing. Knowing the field the soil came from tells you more than any home test. Ask.
The cap and the hardscape, locally
The premise that Armenian hardscape supply is almost nonexistent needs splitting in two. Sixteen stone types and one wood listing at the main specialist shop20, on top of a volcanic highland you can collect from for free. Stone is solved locally. Wood is the piece to plan around, and it travels light enough to carry in.
Geological hardscape is abundant, because this is a volcanic country. Volcanic scoria is a porous inert silicate with huge surface area21, excellent as bulk filler under the soil layer to save soil volume and keep the deep layer permeable, and it doubles as biological filter media. Hrazdan and Kasakh river gravel is predominantly volcanic and inert21: sieve for a 2 to 4 mm fraction and wash it until the water runs clear, and that is your cap for nothing. Volcanic tuff, the national building stone, is silicate and chemically inert, but it is soft and friable and can shed fines for a long time21, so test any piece in a bucket for a week. And beware the naming trap: some Armenian tuff is calcareous travertine, which will raise your hardness.21 See the carbonate ceiling for what that actually costs you.
So the correct Armenian build is lava rock or coarse scoria as bulk fill at the back to build the slope, local mineral soil over it, river gravel cap, tuff or river stone for the visible hardscape, and imported wood only if you can get it.
And a concrete piece of shopping advice. The specialist range in Yerevan runs to 77 plant items and includes almost everything this method wants: about twenty Anubias forms, about twelve Microsorum, several Cryptocoryne, Vallisneria, Bacopa, Ludwigia, Echinodorus and Hygrophila, at roughly 1,000 to 5,000 AMD each, sold loose and unbranded.20 It also stocks the carpet plants this method cannot grow. Do not buy those for a soil tank. That single sentence will save a beginner money on their first attempt.
Honest about the setup
The first month is a race between the rooted plants and the soil chaos, and the plants have to win.
That is her own framing, from April 20265. Here is what the race looks like from outside the glass. Almost every failure of this method happens in this window, and almost all of it is survivable if somebody tells you in advance that it is normal.
Week 1. The water goes cloudy, sometimes milky, sometimes brown. Ammonia reads high and may read very high. There may be a surface film and a smell. Bubbles rise from the substrate. Some plants melt, particularly Cryptocoryne and anything grown emersed at the nursery, which is most of them. All of this is expected. Short day, six hours or a split three and three. Test ammonia daily. Skim the film. Do not add fish, fertiliser or bacteria bottles.
Week 2. Cloudiness peaks and starts to clear. Ammonia is often still measurable. Diatoms, a brown dust on the glass, usually appear. Floaters should be visibly growing; if they are not, something is wrong. Do a 50 percent water change if ammonia is above about 2 mg/L. This is where the hobby's version of her method gives bad advice, because it treats water changes as forbidden. They are not. She does them when there is a reason, and in week two there is a reason.
Week 3. Green water or a green film on the glass is common. New submersed leaves should be appearing on the stems. Roots are establishing and ammonia should be falling. Wipe the front glass only and leave the back and sides. Consider a few snails. Do not increase the light.
Week 4. Her own marker. Plant growth should be clearly good. If ammonia has read zero for a week and the plants are growing, add the first fish, and add few. Three or four small hardy ones, not a full stocking. Feed them normally, because the food is the fertiliser. Do not add anything sensitive, and do not add shrimp yet if you have any copper doubt.
Weeks 5 and 6. The tank stabilises. The fast stems need their first trim. Floaters need thinning, or they take over. A biofilm haze on surfaces is normal and is food. Prune, add the rest of the stock gradually, and start reading the tank rather than the calendar.
If it goes wrong. Persistent high ammonia means the soil was too rich, and it is fixed by large water changes and patience. Dying plants with clear water and zero ammonia means the soil was too poor, and it is fixed the way she fixed it in 2026: push richer soil or fertiliser pellets down into the layer, then do a 30 percent change to clear the disturbance.4 The one unrecoverable failure is a soil that smells of rotten eggs or of chemicals. Start again with different soil.
Then the routine. Top up evaporation, but not with more tap water than you need or hardness will climb. Prune, which is the actual maintenance and is more work than people expect in a tank that is growing well. Water changes when there is a reason rather than on a calendar; her own tanks go six months or more1, and a beginner's should go a month or two at first. Feed the fish properly, because underfeeding a soil tank starves the plants. Do not vacuum the substrate. Expect to add nutrients eventually, because a soil layer is a reservoir and not an infinite one. And expect some algae permanently, because her stated goal is control, not eradication.
Media boxes on this site are 5 to 2, and this banner is 16 to 5. Both sit inside the range measured on grand prize photographs, which run 1.9 to 1 up to 3.4 to 1 and cluster between 2.4 and 2.923.
One more misquote
"Walstad says plants get their carbon from the soil."
This one is interesting because it is not a fabrication. It is a promotion. Something she treats as a minor entry in a list gets repeated until it becomes her headline argument. Sediment CO2 uptake is the fourth of five carbon acquisition adaptations in her carbon chapter, occupying roughly one page of a 225 page book. In her own one paragraph summary of that chapter she names two strategies, and sediment CO2 is not one of them.1
Her answer to how you get carbon without injecting is a whole different chapter, called "Aerial Advantage", whose first section is about air CO2 uptake being more efficient.1 Emergent growth, floating leaves, heterophylly, open tops. Not the soil.
And her own published literature index records the correct reading of the primary evidence, with the qualifiers attached: uptake by plants other than isoetids is substantial in carbon poor habitats, correlates with root porosity, small size and low water CO2.319 The hobby's version is her statement with the qualifiers deleted. The full verdict, with the numbers, is on the cycling page.
- Walstad, Diana L. Ecology of the Planted Aquarium. Fourth edition, April 2023, Echinodorus Publishing, 225 pages, ISBN 979-8-9875741-0-2. The 23 page preview is open access and contains the full table of contents and Chapter I. Preview PDF
- Walstad, Diana. Nitrogen Uptake by Aquatic Plants. 2017, reissued 2023. Open access, 6 pages, with its own reference list to the primary literature. The filter removal account and the nitrification stoichiometry. PDF
- Walstad, Diana. Aquatic Ecology Subject Index. 2023. Open access, 175 pages, roughly 1,490 author-year citations arranged by topic. Effectively the book's bibliography, published separately and free. PDF
- Walstad, Diana. "Fertilizing Substrates." Blog, 20 April 2026. Open access. The Piedmont clay and bone meal soil, the frozen soil cube technique, the fertiliser sticks and the 30 percent water change. dianawalstad.com
- Walstad, Diana. "One Month after Tank Setups." Blog, 29 April 2026. Open access. The no filter and no aerator statement, the race against time and soil chaos framing, the potting soil that failed at NPK 0.08 / 0.03 / 0.06, and the heavy Vallisneria trimming. dianawalstad.com
- Walstad, Diana L. "Scientific Papers." Open access, one page, listing fifteen peer reviewed papers 1970 to 2001 and stating her BSc in Microbiology, University of Kentucky, December 1967. PDF
- Walstad, Diana. Potted Plants for Fish Breeding Tanks. 2023. Open access, 10 pages. The breeding tank configuration. PDF
- The Aquatic Gardener index, 1985 to 2026. Free to read. Filtered to her name it returns 53 items between 1991 and 2023: 25 substantive articles plus 28 question and answer columns, including the four part allelopathy series of 1995 and 1996 and "Bicarbonate as a Carbon Source" in 2023. aquatic-gardeners.org
- Gross, Elisabeth M. "Allelopathy of Aquatic Autotrophs." Critical Reviews in Plant Sciences 22 (2003): 313 to 339. The standard review of the field, published seven years after her series. Paywalled at the publisher, free green copy at Konstanz Gross is one of the scientists she thanks for reviewing her manuscript. DOI 10.1080/713610859
- van Donk, Ellen and van de Bund, Wolf J. (2002). Impact of submerged macrophytes on phyto- and zooplankton communities: allelopathy versus other mechanisms. Aquatic Botany 72: 261 to 274. The sceptical review. Paywalled. DOI 10.1016/S0304-3770(01)00205-4
- Barko, John W. and Smart, R. Michael (1986). Sediment-related mechanisms of growth limitation in submersed macrophytes. Ecology 67(5): 1328 to 1340. Paywalled. The standard reference for the finding that growth does not rise without limit with sediment richness. DOI 10.2307/1938689
- Shahinyan, H. V. (2005). On the hydrogeochemical characteristics of some drinking waters supplying the city of Yerevan. Proceedings of NAS RA, Earth Sciences LVIII(1): 41 to 45. Sampling 2002 to 2004. Open access PDF. The source for every Yerevan water figure on this page. arar.sci.am
- Tepanosyan, G. and others (2017). Human health risk assessment and riskiest heavy metal origin identification in urban soils of Yerevan, Armenia. Chemosphere 184: 1230 to 1240. Paywalled; the abstract is open and states the findings. DOI 10.1016/j.chemosphere.2017.06.108
- Tepanosyan, G. and others (2024). Compositional-geochemical characterization of lead anomalies and lead-induced human health risk in urban topsoil. Environmental Geochemistry and Health 46: 192. Yerevan, Gyumri and Vanadzor. Paywalled; abstract open. DOI 10.1007/s10653-024-01984-7
- Pipoyan, D. and others (2025). First geochemical insight into phosphorus concentration, origin and spatial distribution in the soils of the Ararat Valley. Environmental Monitoring and Assessment 197: 1224. Phosphorus 493 to 1,932 mg/kg, mean 891. Paywalled; abstract open. DOI 10.1007/s10661-025-14675-2
- Pipoyan, D. and others (2026). Micronutrient contents and soil-to-plant transfer in agricultural lands of the Ararat region, Armenia. Environmental Health Insights 20. Open access. Soil zinc 55.6 to 219 mg/kg, copper 42.1 to 189 mg/kg. This is the copper warning. DOI 10.1177/11786302261457694
- Poghosyan, Z. and others (2025). Geochemical characterization and human health risk assessment of arsenic in soils of a high background area, Lori region, Armenia. Environmental Research 285: 122356. Paywalled; abstract open. DOI 10.1016/j.envres.2025.122356
- Tepanosyan, G. and others (2026). Arsenic and lead in soils of Shirak region, Armenia. Environmental Geochemistry and Health 48: 443. Open access. Mean soil arsenic 15.1 mg/kg, mean lead 12.5 mg/kg. DOI 10.1007/s10653-026-03348-9
- Winkel, A. and Borum, J. (2009). Use of sediment CO2 by submersed rooted plants. Annals of Botany 103(7): 1015 to 1023. Open access. The study her own index cites, and the source of the qualifiers the hobby drops. DOI 10.1093/aob/mcp036
- Gazanik, the specialist shop in Yerevan, read from its own published product catalogue. The eleven item substrate range, the ISTA Premium Soil price, the sixteen stone types, the single driftwood listing, the seventy seven plant lines and the 1,000 to 5,000 AMD plant prices are counts read straight from the shop database on 8 September 2026, not from anyone's description of the shop. The same reading is set out in full on the Armenia page. gazanik.am published product catalogue and gazanik.am. The Armenian terminology (հատակաշերտ, սննդահող, հող) is from the hub glossary at /armenia/glossary/, where each term is marked as established, a Russian loan, or newly proposed.
- Հայերեն Վիքիպեդիա, the Armenian Wikipedia rock articles. Բազալտ (basalt), Հրաբխային տուֆ and Տուֆ (volcanic tuff), Հրաբխային խարամ (volcanic scoria) and Խարամ (furnace slag), Տրավերտին (travertine). Used for rock composition, the silicate versus carbonate distinction, the Armenian names, and the tuff and tufa naming trap. Each article sources its own primary geological literature. The full reading, including the wrong cross-language link between Տուֆ and tufa, is on the Armenia page. hy.wikipedia.org
- Our own arithmetic. Not a published source. One, every dGH and dKH figure attributed to Shahinyan on this page. He prints hardness only in mg-eq per litre; we convert at 1 mg-eq/L = 50.045 mg/L as CaCO3 = 2.804 dGH. That covers the 2.9 to 10.9 dGH range, the 2.9 to 3.8 for Avan, Kanaker and Nork, and the up to 10.9 for Davtashen. Two, the KH figure is not measured and nobody publishes one for Yerevan. The about 3 to 11 dKH is our estimate from the published bicarbonate share of the anions, checked against one bottled water label. Verify it with a test kit. Three, the cost comparison: a 60 by 30 cm tank with a 5 cm bed is 9 litres, two 8 litre bags at roughly 24,000 AMD each is about 48,000 AMD, and 2.5 to 4 cm of soil plus the same of cap in that footprint is roughly 5.5 litres of each. Four, the soil sourcing ranking is our judgement applied to the published contamination surveys, not a finding in any of them. calculated, repeatable, unverified by a third party
- Aspect ratios of grand prize aquascape photographs, measured. Intrinsic
widthandheightattributes read off the shipped<img>tags of the IAPLC grand prize archive, twelve photographs: 3.27, 2.83, 1.90, 2.20, 2.57, 2.84, 3.13, 3.21, 2.39, 2.50, 2.84 and 3.44 to 1. Hence the 1.9 to 3.4 range and the 2.4 to 2.9 cluster. Recorded in our own reading of Source page iaplc.com/j/grand_prize_works measured, repeatable against the live page - The edition confusion, checked. There is no 2025 or 2026 edition of Ecology of the Planted Aquarium; the author's own site gives the fourth edition as April 2023. Walstad did publish a separate and different book, Aquarium Fish Reproduction, in 2025, which is the likely origin of the error now appearing in retailer listings. dianawalstad.com/aquariums. Earlier editions are recorded at Open Library from 1999, but the catalogue does not cleanly attach each ISBN to an edition, so no earlier ISBN is quoted here. author's own site, read 8 September 2026
Continue
Where to go next.
Water changes
Where the Walstad position on water changes meets the arithmetic, and the exact point the two agree.
Nitrification, decomposition and roots
Root uptake, oxygen leaking out of roots, and why the substrate is doing more than the filter.
The windowsill tank
A soil tank on a sill, which is the Walstad idea at its smallest and cheapest.
Find a plant
Which plants will actually do this, filterable on light and carbon.
Choose a substrate
Compare capped mineral soil with aquasoil and inert sand before choosing the build.