20-Gallon High-Tech Iwagumi Aquascape (Intermediate)
A 20-gallon Iwagumi: a few stones, one carpet, and a great deal of deliberate empty water. It is a standard tank size, and the easiest bracket to get right. Pressurised CO2, active soil and real light — faster growth, more colour, and a tank that needs you every week. 1 plant species, Seiryu Stone, and 4 livestock groups checked against each other for compatibility — every quantity below sized to 20 gallons and every plant chosen for an intermediate.
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Everything below is generated for this 20-gallon Iwagumi build — 1 plant, 4 livestock groups, and gear sized to 20 gallons. The studio does the same for your tank, free.
Hardscape — what to buy and how to place it
Seiryu Stone is blue-grey, sharply angular, cut through with white calcite veins that run the same way on every piece. Seiryu is a carbonate rock, so it slowly raises KH, GH and pH. That suits most community fish and is worth knowing if you are keeping soft-water species — test your KH a fortnight after filling rather than assuming your tap numbers still apply. Keep every stone’s veins running in the same direction; it is the single thing that makes a group read as one broken rock rather than several unrelated ones.
At 20 gallons, plan on three to five pieces in clearly unequal sizes. An odd count is easier to compose, and one piece should obviously lead — a group of similar-sized pieces spread evenly across the tank is the most common way a first scape goes flat.
Set the stones before a single plant goes in, and view the tank from where you will actually sit rather than from directly above. Bury a third of each stone so it looks like it grew there instead of being placed there, and angle the faces slightly toward the front glass so light catches them.
Substrate
Aqua soil (e.g. ADA Amazonia / UNS Controsoil), built to about 2–3" and sloped higher at the back. Active soil buffers soft, slightly acidic water and feeds roots. Slope higher at the back for depth.
Fresh aqua soil leaches ammonia for the first one to three weeks. That is normal and it is also why you do not stock a high-tech tank early: run it, change a good volume of water two or three times in that first fortnight, and wait for ammonia and nitrite to read zero before any livestock goes in.
The whole floor of this tank is Glossostigma elatinoides, so the substrate contour IS the layout — there is no background planting to hide a flat bed. Build a real slope from front to back and let the carpet run up and over it; that rise is what gives an otherwise open tank its depth. Plant in small clumps a couple of centimetres apart and let them spread sideways to meet, rather than packing them in to look finished on day one.
Plant list & placement
Plant back to front, into damp substrate with the tank only part-filled — it is far easier than fighting buoyancy in a full tank. Glossostigma elatinoides is the tallest thing in this plan at around 1", so it sets your back row and everything else steps down in front of it.
Glossostigma elatinoides is the fast grower here — classic high-tech carpet plant. Tiny round leaves form a dense, vivid green mat. Strong light required or it grows upward rather than carpeting. A staple of Amano-style Iwagumi layouts. Expect to be cutting it weekly once it establishes. Top the stems, replant the healthy tops in the same group and discard the old bases; a stem bed replanted from tops stays dense, while one left to grow on goes bare at the bottom.
Stocking
This stocking is built to spread through the tank rather than crowd one layer: Cardinal Tetra works the open middle water, Honey Gourami works the surface and Julii Cory works the floor. A tank where every fish occupies the same band looks half-empty even when it is fully stocked, and the fish themselves compete more.
Keep Cardinal Tetra in 6 or more and Julii Cory in 6 or more. These are not decorative numbers — a shoaling fish kept in threes spends its life stressed, colours down and hides, and people then conclude the species is dull. The counts in the list above are already scaled to this tank.
Honey Gourami is the centrepiece. Gentle, smaller and far more peaceful than dwarf gourami; great centerpiece.
Olive Nerite Snail is the clean-up crew, and in a planted tank it earns its place — grazing biofilm and soft algae off the hardscape and leaves faster than you can. Add it last, once the tank has some algae to eat, and drip-acclimatise rather than dumping the bag in.
- Cardinal Tetra — Keep Cardinal Tetra in a group of at least 6 — kept in ones or twos they get stressed, shy, and nippy.
- Honey Gourami — Honey Gourami is territorial/solitary — best kept as a single specimen.
- Julii Cory — Keep Julii Cory in a group of at least 6 — kept in ones or twos they get stressed, shy, and nippy.
These species are close enough in size and temperament that none of them out-competes another at feeding time, which is the quiet reason a lot of communities fail. Every pairing was run through Skapelab’s compatibility engine and anything returning even a caution was swapped out rather than published. Check any substitution you make there before you buy.
Equipment
| Category | Recommendation | Notes |
|---|---|---|
| Filtration | Fluval 207 Canister Filter | ~$105–140 |
| Lighting | Chihiros WRGB II 30 | ~$105–140 |
| Co2 | CO2Art Pro SE Series Regulator + 5lb Cylinder | ~$145–185 |
| Heating | Hygger 200W Titanium Heater with Controller | ~$32–48 |
| Substrate | Mr. Aqua Aquarium Soil 9L | ~$32–46 |
| Fertilizer | Estimative Index DIY NPK Dry Ferts Kit | ~$28–45 |
| Testkit | API Freshwater Master Test Kit | ~$28–42 |
| Water treatment | Seachem Prime 500ml | ~$12–20 |
| Bacteria | Seachem Stability 250ml | ~$8–14 |
What the first two months look like
| Week 1 | Hardscape in, planted, filled and running with no livestock. CO2 comes on an hour before the lights and off an hour before they go out; aim the drop checker at a green, never yellow. Keep the photoperiod short, around six hours, while the plants root. |
| Weeks 2–4 | Cycling, and the ugly phase. Brown diatom dust on the glass and hardscape is normal in a new tank and passes on its own once silicates are used up; the fresh soil is also still releasing ammonia, so keep changing water. Some plants will melt back and regrow in their submersed form — that is conversion, not death, so trim the mush and leave the roots. Do not stock until ammonia and nitrite both read zero. |
| Weeks 4–6 | Stocking begins, a few animals at a time with a fortnight and a water test between additions. The carpet should be visibly running now; resist raising the light to hurry it. |
| Months 2–3 | The scape fills in and the routine settles into the schedule below. Judge the design now rather than on day one; a planted tank is not finished until it has grown into itself. |
Care schedule
| Daily | Feed lightly — as much as they clear in a minute or two — and take ten seconds to count heads and look at the plants. Check the drop checker is green before the lights come on. |
| Weekly | 40% water change — about 8 gallons on this tank — using a siphon and a bucket. Dose your macros and micros after the change, not before. Wipe the glass and check the CO2 cylinder pressure. |
| Monthly | Rinse filter media in old tank water — never under the tap, which kills the bacteria colony you spent six weeks growing. Test KH, GH, pH and nitrate. Check for anything the weekly routine keeps missing behind the hardscape. |
| Every few months | Replace the CO2 diffuser membrane, check the regulator has not crept, and pull the deepest stems for a hard replant. Lights lose output long before they fail — plan on replacing LEDs or bulbs on a schedule, not on symptoms. |
Make it yours
This is a starting point. Open it in the studio to swap plants, resize to your tank, and get a hand-illustrated render, placement diagram, and shopping list — free.
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