This page decides one thing for a 3–10 gallon tank without CO2: what goes under and into the water so your plants grow. Pick your tank in the Tank Facts panel above; the answer changes with your substrate and your plants.
Why forum answers disagree
Most arguments about root tabs and aquasoil skip one fact: plants feed in two different ways. Rooted plants — crypts, sword plants, bulb plants, carpeting plants — take most of their food through the roots, from the substrate. Rhizome plants — java fern and anubias, plus mosses and floaters — take it from the water. Aquarium Co-op says rooted plants “all tend to feed from the substrate”, while plants such as anubias and java fern “typically do not use root tabs as much”.
So the right answer depends on what you plant, not on which substrate is “best”.
Sand + root tabs, aquasoil, liquid fertilizer
| Option | What it does | What the maker says | Fits when |
|---|---|---|---|
| Sand or gravel | Holds roots, adds no food | Aquarium Co-op: an inert substrate “doesn’t contain any nutrients on its own” | You add root tabs for rooted plants, or you grow only rhizome plants |
| Root tabs | Fertilizer capsules pushed into the substrate under the roots | Co-op: one every 5–6 in in a grid, more about once a month. Seachem: 6 for a standard 10 gallon, new ones every 3–4 months | Crypts, swords and other rooted plants in sand or gravel |
| Aquasoil (e.g. Fluval Stratum) | A soil substrate that starts with nutrients | Fluval: nutrients deplete and the soil compacts; replace every 1–2 years; may raise ammonia slightly in a new tank | You plant many rooted plants and accept replacing the substrate later |
| Liquid fertilizer | Feeds plants through the water | Co-op Easy Green: once a week in low light, twice in medium light | Java fern, anubias, mosses, floaters — and as a top-up for everything |
How many root tabs
| Tank | Rule | Tabs | Replace |
|---|---|---|---|
| 5 gallon | one every 5–6 in (Co-op grid) | 3–4 | Co-op: about monthly · Seachem: every 3–4 months |
| 10 gallon | “A standard 10 gallon aquarium requires 6 tabs.” (Seachem) | 6 | same as above |
| Densely planted | Co-op: “every 4 inches (10 cm) or closer” | more | same as above |
Push each tab deep, close to the roots, and quickly so it doesn’t start dissolving on the way down — Co-op says to insert them “as quickly and deeply as possible”. The two brands give different replacement intervals; use the one on your package.
How much liquid fertilizer
| Product | Maker’s dose | 5 gal | 10 gal |
|---|---|---|---|
| Easy Green, 120 ml bottle | 2 drops per gallon; once a week in low light, twice in medium light | 10 drops | 20 drops |
| Easy Green, 500 ml bottle | 1 ml per 10 gallons (measuring cap) | 0.5 ml | 1 ml |
| Seachem Flourish | 5 ml (1 capful) per 60 US gallons, once or twice a week | — | — |
| 2Hr Aquarist APT 3 | 3 ml per 100 L per day; for tanks without CO2 the maker points to its dosage calculator | — | — |
The 5 and 10 gallon columns are the maker’s rule multiplied out; where a dose is per 60 gallons or per 100 liters, we leave the math to the maker’s own calculator rather than round it for a nano tank. 2Hr Aquarist adds a rule worth keeping: “when in doubt, dose slightly less, not more.”
Java fern and anubias: don’t bury the rhizome
Both grow from a thick horizontal stem, the rhizome. Tropica says to grow java fern “on a root or stone, attached with fishing line until it has gained a hold” and, for anubias, that the rhizome “must not be covered because it tends to rot”. That is why these two need no root tabs and no aquasoil: their food comes from the water.
If you are about to buy aquasoil
Fluval says Stratum “has the potential to slightly increase ammonia levels” when added to an aquarium, which “should not present a problem” in an established tank. In a brand-new nano tank that means letting it run before adding animals. Rinse it gently in a colander, Fluval says, without stirring it up. To know how many bags to buy, the substrate calculator applies Fluval’s own formula to your tank’s length, width and bed depth.