Best substrate for a no-CO2 nano tank
Building a planted nano tank without a CO2 cylinder is absolutely doable, and the substrate plays a key role. The question comes up all the time: do you really need a pricey “aquasoil” in such a small, no-CO2 tank? Here’s what it actually brings to the table, and how to choose.
The bottom line. In a no-CO2 nano, a proper aquasoil is a real plus: it feeds the roots and often lowers the pH, which favours easy plants. Aim for 3 to 5 cm deep, don’t rinse it, and fill the tank very gently. It isn’t mandatory (inert sand plus fertilising works too), but it’s the simplest way to plant with peace of mind.
What an aquasoil actually does
An aquasoil isn’t just decorative gravel. It works on two fronts:
- Root nutrition: it’s loaded with nutrients that plants draw up directly through their roots, which is handy when you aren’t dosing CO2.
- Water chemistry: most aquasoils lower the pH and slightly soften the water, conditions that plenty of plants and shrimp love.
Without CO2, your plants grow more slowly: a good substrate partly makes up for it by giving them easy access to nutrients. It’s the natural ally of easy plants (Anubias, Cryptocoryne, mosses, sturdy stems).
In a nano, don't overdo it: a quality aquasoil plus easy plants plus moderate lighting is more than enough. Stacking aquasoil, CO2 and intensive dosing onto 20-30 litres is the surest way to trigger an algae outbreak. Simplicity wins.
Aquasoil or inert sand?
| Option | Upsides | Limits |
|---|---|---|
| Aquasoil | Feeds the roots, lowers pH, ideal for plants | Cost, runs out (1-2 years), cloudy water at first |
| Inert sand / gravel | Cheap, neutral, lasts forever | Adds no nutrients → fertilising is a must |
| Aquasoil + thin sand cap | Good looks + nutrients | A little more fiddly to set up |
For a planted no-CO2 nano with no fuss, aquasoil on its own is the simplest choice. If you’re mostly after attached plants (Anubias, mosses on rocks/wood), inert sand can do the job.
Setting it up properly
Pick an aquarium aquasoil suited to small volumes: a 3-litre bag usually covers a nano.
Aquasoil for a planted nano
Our pick- Feeds the roots, useful even without injected CO2
- Often lowers the pH and softens the water (easy plants, shrimp)
- A 3-litre bag usually covers a nano (3 to 5 cm)
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After a year or so, once the substrate starts to run out, root tabs get growth going again without rebuilding the nano.
Root tabs (root fertiliser)
Our pick- Restarts root nutrition once the substrate is depleted
- Tabs you push discreetly into the substrate near the plants
- Extends the life of an aquasoil without tearing everything down
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Before laying the substrate in your nano, run through these points:
- I've allowed for 3 to 5 cm of substrate across the bottom of the nano
- I do NOT rinse the aquasoil
- I fill the tank very gently (plate/bag) to avoid clouding the water
- I accept cloudy water for the first few days (normal)
- I've picked easy plants suited to a no-CO2 setup
- I plan to add top-up fertilising after a year
For a first planted nano, aquasoil is worth the money: it forgives a shaky start by feeding the roots. Its only real downside is the cloudy water of the first few days, which a little patience and a running filter soon sort out.
Conclusion
In a no-CO2 nano, an aquasoil isn’t essential, but it’s the simplest route to healthy plants: it feeds the roots and sets up water that plants like. Aim for 3 to 5 cm, don’t rinse it, fill gently, and pair it with easy plants. You’ll get a lovely nano without any complicated kit.
For choosing plants, read Easy plants with no CO2 for beginners. And for the whole scape, our Aquascaping silo pulls our guides together.
Frequently asked questions
Is an aquasoil worth it without injected CO2?
Yes. An aquasoil feeds the roots and often lowers the pH, which helps plants even without CO2. It won't replace CO2 for very demanding species, but it makes a real difference for the easy plants you'd put in a nano.
How deep should the substrate be in a nano tank?
Aim for roughly 3 to 5 cm of substrate across the bottom of a nano. That's enough to anchor the roots and store nutrients, without eating too much into the already limited water volume of a small tank.
Do you need to rinse aquasoil before using it?
No, you don't rinse aquasoil: the granules would break down. Lay it in dry, then fill the tank very gently (pouring onto a plate or a bag) so you don't kick up a cloud. Cloudy water for the first few days is completely normal.
Does aquasoil run out over time?
Yes, an aquasoil releases its nutrients over roughly 1 to 2 years. After that it still anchors the roots, but you top up with fertilisers (root tabs or liquid) to keep growth going.
