How to Set Up a Planted Aquarium, Step by Step

The short version

• A planted aquarium is built in one order: substrate first, then hardscape and plants, then water, then a 4 to 6 week cycle, and only then fish.
• The two decisions that carry the tank are the substrate under it and the light over it. Get those right and the plants do most of the rest.
• A 10-gallon is the most forgiving first size: enough water to stay stable, cheap enough to redo if you learn something the hard way.
• Below: the layers, a medium-light target of 30 to 50 PAR, the beginner plant list, the cycle, and what to stock once it holds.

A planted aquarium is built in one order that does not bend: substrate, hardscape, plants, water, weeks of waiting, then fish. Skip ahead to the fish and you spend the next month fighting ammonia and algae instead of watching new leaves unroll.

The better news is that a low-tech planted tank asks for less gear than the hobby likes to sell you. No pressurized CO2, no fertilizer routine, no reactor. A bag of substrate, one honest light, a handful of hardy plants, and a test kit will grow a tank you can stock in about six weeks. Here is the whole build.

Start with the substrate, because you cannot swap it later

The substrate is the one layer you cannot change without tearing the tank down, so it is the first decision. For a planted tank that feeds its own plants, aquasoil is the default: a baked, nutrient-loaded clay that also softens and acidifies the water toward pH 6.5, which suits soft-water plants and shrimp. Lay it 2 to 3 inches deep, sloped higher at the back so the scape has some depth to it.

The one catch with fresh aquasoil is that it leaches ammonia for the first few weeks. That is fine, because you are going to cycle the tank before any animal goes in anyway, and that early ammonia even feeds the cycle. If you would rather run plain inert sand, you can, but then you feed root-hungry plants with root tabs pushed under the rosettes every few months.

Light is the throttle, so aim for 30 to 50 PAR

Light drives plant growth, and it drives algae just as hard, which is why more is not better. A full-spectrum LED bar set to roughly 30 to 50 PAR at the substrate grows the widest range of low-tech and medium-light plants without tipping the tank into an algae farm. Above that, with no CO2 to match, the extra light feeds algae instead of leaves.

Put the light on a timer for 6 to 8 hours a day, not the 10 to 12 a bright display tank in a shop runs. A shorter photoperiod on a new build is the cheapest algae insurance there is. You can stretch it later once the plants are established and pulling nutrients hard.

The plants that make it forgiving

Plant heavily from the first day and weight the list toward easy, hardy species. Three plants carry most beginner tanks. Java fern (Microsorum pteropus) is an epiphyte you tie to wood or rock (bury the rhizome and it rots), rated for 68 to 82 F and low light, and it is close to unkillable. Cryptocoryne wendtii (Cryptocoryne wendtii) is a rooted midground crypt for 72 to 82 F that will drop every leaf in a sulk after planting, then regrow from the roots in two to three weeks: do not pull it.

Add a fast stem to soak up nutrients while the tank finds its feet. Hornwort (Ceratophyllum demersum) grows in almost anything from 59 to 86 F and pulls ammonia so fast it doubles as cycling insurance. The fast growers are the ones out-competing algae in the fragile first month, so a new tank should be over-planted, not under.

The build, step by step

1. Rinse the tank, set it level on its stand, and dry-fit your hardscape (wood and rock) before any substrate goes in.
2. Add substrate: 2 to 3 inches of aquasoil, sloped up toward the back.
3. Set the hardscape into the substrate so it sits solid, not perched on top.
4. Plant heavily while the substrate is just damp: epiphytes tied to hardscape, rooted plants and stems into the soil.
5. Fill slowly onto a plate or a plastic bag so you do not blast craters in the substrate. Add dechlorinator to neutralize the chlorine and chloramine in tap water, which otherwise kill the bacteria you are about to grow.
6. Start the light at 6 hours a day on a timer, and let the tank run empty.

Cycle it before a single fish

A new tank has no bacteria to process fish waste, so it has to cycle first: grow the colony that turns ammonia into nitrite and nitrite into nitrate. With a liquid test kit you watch ammonia rise and fall, then nitrite rise and fall, then nitrate appear. When ammonia and nitrite both read zero and nitrate is present, the tank is cycled, usually 4 to 6 weeks in.

A heavily planted tank shortens this because the plants eat ammonia directly, so your readings may stay low the whole way through. That is a good sign, not a reason to skip the test. Wait for two zero readings a few days apart before you buy a fish.

What goes wrong: algae and impatience

Two failures account for most dead beginner tanks. The first is algae, and it almost always traces to the same cause: too much light over too few plants, often for too many hours. The fix is not a bottle, it is the balance. Cut the photoperiod to 6 hours, add fast plants, and let the tank catch up over two to three weeks.

The second is stocking a tank that has not cycled. Fish put into an uncycled tank sit in their own ammonia, and beginners read the resulting stress as an illness rather than a build step they skipped. The cost is measured in dead fish, and it is entirely avoidable by waiting the six weeks the cycle takes.

Stocking a planted tank once it holds

Stock light and add in stages. A cycled, planted 10-gallon can carry a small centerpiece plus a nano school plus a cleanup crew. A honey gourami at 2 inches makes a calm centerpiece; a school of six harlequin rasbora (Trigonostigma heteromorpha) fills the mid-water. A colony of cherry shrimp (Neocaridina davidi) and a nerite snail (Neritina sp.) graze algae and leftover food as the cleanup crew.

Self-sustaining does not mean hands-off. The plants and bacteria filter the water, but you still top off evaporation, feed lightly, prune the stems when they hit the surface, and do a water change if nitrate climbs past 40 ppm. The biology does the filtering; the keeper still keeps.

Frequently asked questions

Do you need CO2 for a planted aquarium?

No. Plenty of planted tanks run with no injected CO2 at all, on low-tech and medium-light plants like java fern, crypts, and Anubias. CO2 speeds growth and lets you keep demanding carpet plants, but it also raises the light and nutrient demand and the algae risk with it. A first tank is easier and cheaper without it.

How long before you can add fish?

Plan on 4 to 6 weeks, gated by the test kit rather than the calendar. The tank is ready for animals when ammonia and nitrite both read zero and nitrate has appeared, held across two readings a few days apart. A heavily planted tank sometimes cycles faster, but you still confirm it with a test rather than a guess.

What is the easiest substrate for a beginner?

Aquasoil is the most forgiving because it feeds the plants for you and buffers the water toward pH 6.5. Plain inert sand is cheaper and works too, but then you supply root nutrients with root tabs every few months. Avoid deep gravel with nothing under it, which starves rooted plants.

Why is my new planted tank growing algae?

Almost always too much light for the plant mass, often over too long a day. On a new tank, cut the photoperiod to 6 hours, make sure it is heavily planted with fast growers, and give it two to three weeks. Some algae in the first month is normal while the plants establish; persistent algae is a light-and-nutrient balance problem, not a reason to buy an algaecide.

Once the tank is cycled, every choice left is a compatibility question: which fish suit your water, how many the volume holds, and which plants will grow under your light. Run the build through the build planner for a stocked, balanced starting point, check any species against the compatibility database, and if you want to start smaller, read the 5-gallon planted tank or 10-gallon planted tank guides in the build-guide library. New to layout, start with aquascaping for beginners.