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The criterion nobody applies
Almost every “easy aquarium plants” list is correct and useless for a nano tank, because easy is not the constraint. Anubias, java fern, crypts and moss are all easy in a 55-gallon too. The constraint in a small tank is final size: a plant that reaches 12 inches is a background plant in a 4-foot tank and a wall in a 5-gallon.
So this page ranks on scale first. Every species below has a published light requirement and a published CO2 requirement, and where the seller publishes a mature height we have used it. Where they do not, we say so - which turns out to matter for the carpeting plant.
If you specifically want plants chosen for a betta - resting shelves, no sharp leaves, surface cover for a bubble nest - that is a different list, ranked on different things. This one is about proportion.
The scale problem, in numbers
| Tank | Typical length | Typical height | Plant height that still reads as “planted” |
|---|
| Rated 5 gal | about 16-20 in | about 10-12 in | Under 6 in, except one deliberate tall corner |
| Rated 10 gal | about 20 in | about 12 in | Under 8 in across the midground |
| Rated 16-20 gal | 24-30 in | 12-16 in | Anything on this page works |
Those tank figures are typical dimensions for the class rather than any manufacturer’s specification, and we would rather label them as our own rounding than pass them off as published. The point survives either way: a Cryptocoryne wendtii that Aquarium Co-Op publishes at “around 8 inches” is a midground plant in a 10-gallon and a hedge across the back of a 5-gallon.
What we ranked these on
Published care data. Whether the seller publishes a PAR range, a CO2 requirement and a mature size. Live plants are the worst-documented category in this hobby and Aquarium Co-Op is a notable exception, which is why every plant here comes from a source that publishes numbers.
Nano-scale fit. Mature size against a 16 to 20 inch tank. This is the criterion that reorders the usual list.
Low-light tolerance. Whether it works under the fixture that came with your kit. Most nano lights are modest, and what a nano fixture actually delivers is a shorter number than the marketing suggests.
Growth rate. Cuts both ways. Fast growth exports more nitrate and covers a scape sooner; it also means trimming a small tank every week forever.
Beginner forgiveness. How the plant behaves when it is planted wrong, moved, or left in the dark for a fortnight.
The four shapes of nano plant
Rhizome plants - anubias, java fern - attach to hardscape and must never have the rhizome buried. They need no substrate at all, which makes them the only plants on this page that work in a bare-bottom or fine-sand tank. They also grow slowly, which in a nano is a feature.
Rooted plants - the crypts - feed through their roots and want either a nutrient-rich substrate or root tabs. They are the plants that make a small tank look furnished rather than decorated, and they are the ones that melt dramatically when you move them.
Carpeting plants - dwarf sagittaria here - spread by runners across the front. Most carpeting species in this hobby want injected CO2 and strong light; dwarf sag is the significant exception, and Aquarium Co-Op publishes it at medium light, 20-35 PAR, with no CO2 requirement.
Moss is its own category: no roots, no rhizome, no substrate, attaches to anything, and provides cover at a scale nothing else does. In a shrimp tank it is not decoration, it is infrastructure - which is why it appears again on our shrimp tank page.
Light is the constraint. CO2 usually is not.
Four of the five plants here are published at 10-20 PAR, which is genuinely low light, and all five are published as needing no CO2. That is not an accident of selection - it is the whole reason these species dominate small tanks.
The one to watch is dwarf sagittaria at 20-35 PAR. That is medium light, and it is the first plant on this list that will notice a weak stock fixture. If your light is the one that came in the kit, take the other four and skip the carpet - the trade-offs are laid out in low light versus CO2 in a nano tank.
The two ways people kill these plants
Burying a rhizome. Anubias and java fern rot from the rhizome up when it is under substrate. Tie them to rock or wood instead - the roots can go anywhere, the rhizome must stay in the water.
Throwing out a melting crypt. Cryptocoryne wendtii melts back to bare stems within a fortnight of arriving in new water. Aquarium Co-Op publishes the advice: leave the roots in the substrate and let it regrow leaves suited to your water. It looks exactly like death and it is not.
Substrate: what each of these actually needs
Anubias, java fern and java moss need no substrate at all. Cryptocoryne wendtii and dwarf sagittaria are root feeders, and Aquarium Co-Op names root tabs or a nutrient-rich planted substrate for both.
The practical consequence in a nano is depth. Root feeders want a couple of inches, which in a small tank is a meaningful fraction of the display height and a meaningful fraction of the water volume - our whole site works off the assumption that substrate and fill line take about 15% of rated volume, and a deep planted substrate is how you get to the high end of that. A 20 by 10 inch base at two inches is 6.6 kg, about 14.6 lb, on Fluval’s published formula.
If you want the plants but not the depth, take the three that attach to hardscape and put sand down for looks. That is a completely legitimate nano scape, and our substrate page covers what each option costs you.
Why java fern is ranked last here
It is a superb plant and it is fifth on this page for one reason: size. Java fern gives a small tank vertical structure faster than anything else here, and it keeps giving it - it throws plantlets off its own leaves and colonizes whatever you tie it near. In a 5-gallon that means a plant you are dividing every few months.
Rank it first for a 16-gallon and last for a 5-gallon. That is the honest answer, and it is exactly why we ranked this page on scale rather than on ease.
What plants actually do for water quality
Less than people claim, in a tank this small, and it is worth being blunt about it. Plants take up nitrate, and slow-growing plants take up very little of it. A nano tank full of anubias is not a tank you can stop doing water changes on.
What plants genuinely provide in a nano is cover, surface for biofilm and bacteria, and competition against algae for the same nutrients. Those are real benefits. Nitrate export at this scale is a bonus, not a filtration strategy - the filtration strategy is the water change schedule.
What we left out, and why
Dwarf hairgrass, Monte Carlo and the other fine carpets. They are the plants people actually want when they say “carpet,” and in a low-tech nano without CO2 they mostly fail slowly. We would rather recommend a carpet that works under a stock light than one that photographs well.
Stem plants as a category. They grow fast, which sounds ideal for nutrient export, and then you are trimming a 5-gallon every weekend and replanting cuttings into two inches of substrate. Some people enjoy that. It is not the low-maintenance nano this site is written for.
Anything sold without published care requirements. That excludes a great deal of what is on the shelf, including most plants sold in sealed tubes, and it is the same standard we apply to heaters and filters.
What we cannot tell you
Whether these will grow in your water. Hardness, pH and what your municipality adds are local facts, and plants respond to them. We also cannot tell you how much PAR reaches the substrate under your specific fixture at your specific depth, because no nano light manufacturer publishes PAR at any depth - an absence we record on every light we list.
