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Long-form guide

Starting a Planted Tank: equipment and setup checklist

Plan a planted freshwater aquarium: tank, filter, heater, light, substrate, CO2, test kits, cycling, and setup order.

Updated August 23, 2026 · How recommendations are checked

The short version

A planted tank needs, in priority order: a tank (start with 20 gallons if you can), a light matched to your plant choices, substrate that fits your water and feeding plan, a filter that circulates water without overwhelming the livestock, a heater sized to the room and target temperature, and a test kit for the parameters you need to follow. Everything else is situational. CO2, extra controllers, and specialized additives can wait until the basic setup is stable.

Use this as the planning pass before buying anything. The decisions compound: tank shape affects lighting and planting room, substrate affects how you feed rooted plants, and stronger light increases the need to keep the rest of the setup in balance.

Tank size: the decision that determines everything else

Twenty gallons is a forgiving starting size. More water volume usually gives you more time to notice and correct a change than a very small tank, while the equipment and water changes remain manageable for many homes.

A 10 gallon can work. Smaller tanks simply leave less room for stocking errors, missed maintenance, evaporation, and room-temperature changes. For a first setup, choose the largest tank you can safely support, maintain, and place on a properly rated stand. A nano tank is better treated as an intentional constraint than as the easiest or cheapest route.

Tall vs long: long is usually easier for planted layouts. Using common nominal dimensions, a 20 gallon long has a 30 × 12 inch footprint, while a 20 gallon high has a 24 × 12 inch footprint. That is 360 versus 288 square inches, so the long has 25% more footprint. Exact outside dimensions vary by manufacturer; Aqueon’s catalog lists its corresponding tanks at 30.25 × 12.5 inches and 24.25 × 12.5 inches. The wider, shallower format gives you:

If you have the shelf space, go long.

Dimensions matter for lighting. For two tanks with similar volume, the deeper one generally asks more of the light at substrate level. Match the fixture to the tank’s actual length and depth, not only its gallon label.

Light: what actually drives plant growth

Light sets the pace for plant growth. Too little can limit growth. More light raises demand for carbon, nutrients, and consistent maintenance, and can make algae harder to manage when the rest of the setup cannot keep up. Match intensity to the plants and the amount of adjustment you want to do.

Lower-demand plants (Java fern, Anubias, many Cryptocoryne, Vallisneria, Amazon sword, mosses): Start with a dimmable planted-tank light and a consistent timer. Begin conservatively, then change one setting at a time based on new growth and algae. These plants are often workable without injected CO₂, but they still need suitable placement and nutrition.

Moderate-demand layouts (many stem plants, swords, and attempted carpets without CO₂): Dimming and scheduling are worth paying for because they let you tune the light without replacing it. Whether a plant carpets or stays compact depends on the whole setup, not the fixture name alone.

Higher-demand layouts (some red plants, demanding carpets, CO₂ injection): Choose a fixture with enough coverage and control for the tank dimensions. Stronger light is not automatically better. It narrows the margin for inconsistent CO₂, fertilization, and maintenance. See the best light for a 20 gallon planted tank guide for the detailed tier breakdown.

Substrate: active or inert

Two schools of thought, both work:

Active soil substrate can supply nutrients and influence water chemistry. The effect depends on the product, source water, tank setup, and age of the substrate. For example, Fluval says Stratum supports neutral to slightly acidic pH and can reduce carbonate hardness, so regular KH testing matters. Do not assume every soil will produce a fixed pH or remain chemically active for a fixed number of years. Good for: rooted plants and setups where the product’s stated water effects match the livestock plan.

Primarily inert substrate such as plain aquarium sand or gravel provides structure rather than a built-in nutrient supply. Root tabs or water-column fertilizer may be needed depending on the plants. Check the exact product rather than treating every bag marketed as planted substrate as chemically identical. Good for: setups where you want water chemistry to come mainly from the source water and deliberate dosing.

Pick active soil only when its stated effect fits your source water and livestock. Pick an inert base when you prefer to manage plant nutrition separately. See Best substrate for a planted tank for the detailed comparison.

Depth: use enough substrate to hold the chosen plants securely, with more depth where larger root systems need it. A front-to-back slope can add visual depth, but support steep sections with hardscape or retaining pieces so the slope does not simply settle flat.

Filter: don’t overthink this

Filter ratings are a comparison point, not a promise of flow inside your aquarium. Media, intake guards, lift height, plumbing, and maintenance all change the delivered flow. Choose an adjustable filter intended for the tank’s size range, then check the actual result: leaves should move gently, debris should reach the intake, and fish or shrimp should not be pinned or forced to hide from the current.

Canisters (Fluval, Oase, Eheim): keep most equipment outside the display and offer flexible media arrangements. They cost more and take more setup work than many hang-on-back filters. Good for keepers who value a cleaner display and are comfortable maintaining hoses and seals.

HOBs (AquaClear, Aqueon): cheaper, simpler, easier to maintain. Visible on the back of the tank. Good for budget builds and most casual keepers.

Sponge filters: gentle intake and simple media make them useful for shrimp and fry. They remain visible in the tank and need an air pump. Good for dedicated shrimp or breeding tanks.

For most first-time planted tank keepers, an HOB like the AquaClear 50 is the right pick. See filter guides for the detailed comparison by tank size and livestock.

Heater: size for the room, not volume alone

Size the heater from tank volume, the coldest normal room temperature, target water temperature, and the exact manufacturer’s chart. Do not treat watts per gallon or 100W for a 20-gallon as universal rules.

Independent monitoring matters. Any heater can stop, drift, or remain on. Use a separate thermometer, follow the installation instructions, and replace a unit that is damaged or operating abnormally.

Dual heaters provide limited redundancy. Two correctly sized units can provide partial heat if one stops. One heater’s thermostat cannot cut power to the other if it remains on; that requires an independent controller with its own probe.

Preset and adjustable heaters both require an independent temperature check. See Best heater for a 20 gallon planted tank for details.

CO₂ (only for high-tech)

Injected CO₂ can make demanding carpets, some red plants, and faster growth easier, but it also adds equipment and another variable to manage. If you want a lower-maintenance tank, start without it and choose plants that fit that setup.

Regulator choice matters because inconsistent pressure can make injection harder to tune. Look for a regulator with a stable working-pressure control, a solenoid if you want scheduled dosing, and a reliable way to monitor the tank. Compare the full kit cost, including cylinder, tubing, diffuser, check valve, and monitoring gear. See Best CO₂ system for a planted tank.

If you’re starting out, skipping CO₂ is reasonable. Grow low-tech plants for a while, learn how your tank responds, then decide whether an upgrade solves a problem you actually have. A planted tank without CO₂ can still look stunning. Anubias on driftwood, a wall of Vallisneria, a carpet of moss. CO₂ can accelerate growth in suitable setups; it does not determine whether a tank is attractive.

Test kit: the diagnostic you can’t skip

For a new freshwater tank, ammonia, nitrite, nitrate, and pH are useful starting parameters. Kits differ in the parameters included, measuring range, resolution, and handling steps. Whether you use liquid reagents or strips, check the package, follow the timing and storage instructions, and use the same method consistently when comparing results.

Test often enough during cycling and after livestock changes to see whether ammonia and nitrite are being processed. Log results. A trend is usually more informative than an isolated reading, and an unexpected result should be repeated before a large correction.

Add GH and KH tests when the livestock or water-management plan depends on hardness, including many shrimp setups. If you inject CO₂, monitor it with methods appropriate to the system rather than treating one KH or pH reading as a complete safety check. See Best test kit for a planted tank.

What you don’t need

An airstone by default. Surface movement from the filter may already provide useful gas exchange. Add aeration when the livestock behavior, temperature, treatment instructions, or an interruption in filtration calls for it.

A UV sterilizer by default. It can be useful for specific waterborne problems when correctly sized and operated, but it does not replace diagnosis, filtration, or maintenance. It also cannot treat organisms that are not passing through the unit.

A chiller by default. First compare the livestock’s temperature requirements with the warmest conditions the room actually reaches. Cooling becomes a separate equipment decision when passive measures cannot keep that setup in range.

A smart controller by default. Monitoring and automation can be useful in more complex setups, but they do not replace independent checks or a sound equipment plan.

Proprietary fertilizer regimens. Brands push complex dosing schedules. A simple all-in-one fertilizer may be enough for many planted tanks; follow its label and watch the plants and algae response.

Order of operations: the setup sequence that works

  1. Confirm the tank and stand. Use a level, verify that the stand is rated for the filled aquarium, and follow the tank maker’s support and leak-check instructions. Plan the hardscape before planting.
  2. Add substrate. Slope it front-to-back. Don’t flatten it. Visual depth comes from slope and terracing.
  3. Install heater and filter. Don’t plug them in yet.
  4. Add hardscape. Driftwood and rocks should go in before plants, since moving them later uproots everything.
  5. Plant with the mature layout in mind. Give fast growers room to expand and place slow growers where they will not be shaded. More healthy plant mass can help at startup, but crowding every species is not a substitute for suitable light and nutrition.
  6. Fill slowly with dechlorinated water. Place a plate or saucer on the substrate and pour onto it to avoid disturbing your planting.
  7. Plug in heater and filter. Let temperature stabilize before adding anything else.
  8. Cycle before adding fish. Use a fishless method with a purpose-made ammonia source and follow its label. Food-based methods are harder to dose and can add unnecessary organic waste.
  9. Follow the test results, not a fixed calendar. The biological filter needs time to develop bacteria that process ammonia. Continue until the chosen cycling method’s completion criteria are met consistently.
  10. Make any needed water change, then add livestock gradually. Match the first group to the tank’s actual capacity and test after additions before increasing the bioload.

Cycling: what it is, why it matters

In the aquarium nitrogen cycle, waste produces ammonia. Established biological filtration converts ammonia to nitrite and then nitrate. Ammonia and nitrite can harm fish, so a new tank needs evidence that the biological filter is processing them before livestock is added. UF/IFAS notes that a biological filter must be allowed to develop the bacteria needed to remove ammonia.

A new setup does not begin with a mature biological filter. Adding the planned livestock load too early can expose fish to rising ammonia or nitrite before the filter can process it.

Fishless cycling lets you develop and verify biological filtration without using fish as the ammonia source. Use a documented method, follow the ammonia product’s dosing instructions, and verify completion with repeat test results.

Common first-tank mistakes

The realistic budget

For a 20 gallon planted tank starting from nothing, these are rough U.S. planning ranges, not live price quotes:

A pressurized CO₂ setup adds a regulator, cylinder, tubing, diffuser, and monitoring equipment. Local cylinder deposits and refill costs vary, so price the full system with a nearby gas supplier before deciding. Fertilizer, test reagents, and replacement plants are separate ongoing costs.

See the correction-channel status.