Build your first
planted aquarium
Start with nothing. End up with something. The whole sequence — where it goes, what to buy, what to plant, and the wait in the middle that almost everybody skips.
Almost every planted tank that fails in its first year fails for the same two reasons: it was bought in one afternoon, and it had fish in it before it was ready for them. Neither of those is a knowledge problem exactly. They are sequencing problems. The hobby is genuinely forgiving as long as you do things in the right order and accept that a few of the steps involve doing nothing at all for several weeks.
This page is the whole order of operations for a first planted freshwater community tank — the kind with a group of small hardy fish, a bed of real plants, and no pressurised gas cylinder anywhere near it. It assumes you own nothing yet. It assumes you want the tank to still look good in a year.
Where something is settled science, we say so. Where the hobby has a strong shared conviction that the evidence does not really support, we say that too. There is a fair amount of the second kind in aquarium keeping, and pretending otherwise does beginners no favours.
Eight phases, in this order
Each one depends on the one before it. You can move faster or slower through any of them, but you cannot swap them around — and the one people are most tempted to skip is phase five.
- 0 Phase 0 Before you buy anything Where it goes, what it weighs, how you will get water to it and out of it, and what the real budget is.
- 1 Phase 1 Choosing the tank Why bigger is easier, and why the footprint matters more than the height.
- 2 Phase 2 The kit Filter, heater, light, test kit. What to oversize, and what you can safely leave until later.
- 3 Phase 3 Substrate & hardscape Inert or enriched, how deep, how to slope it, and why the whole layout is built dry.
- 4 Phase 4 Water in, plants in Filling without wrecking the scape, planting heavily from day one, and expecting melt.
- 5 Phase 5 Cycling — the wait everyone skips Ammonia to nitrite to nitrate, done with no fish present. Usually three to six weeks.
- 6 Phase 6 First fish One small group, hardy species, slow acclimatisation, and quarantine as risk management.
- 7 Phase 7 The first three months A routine that fits in twenty minutes a week, the algae phase, and what normal looks like.
Before you buy anything
The single most expensive mistake in this hobby is buying the tank first and working out where it lives afterwards. A filled aquarium is effectively furniture that cannot be moved. Water weighs a kilogram per litre, and once you add glass, substrate and rock, a modest 60 litre tank lands around 80 kg and a 180 litre tank comfortably clears 230 kg. That is a piano sitting on four small feet.
In most homes the floor is not the limiting factor for a tank under about 200 litres, particularly over a ground floor or across joists rather than along one. Above that, or in an upstairs room, or in an old building, it is worth actually thinking about rather than assuming. Spread the load across joists where you can, and use a stand designed for aquariums — a bookshelf that flexes by two millimetres under load is applying a twisting force to a rigid glass box, and glass does not forgive that.
Two practical things people forget. First, direct sunlight. A tank in a sunny window gets an uncontrolled light period, uncontrolled intensity and daily temperature swings, and the algae will find that combination delightful. Ambient room light is fine; a beam of afternoon sun on the glass is not. Second, water access. You will be carrying water to and from this tank every week for as long as you own it. Twenty metres and a staircase between the tank and the tap is the difference between a routine you keep and one you quietly abandon.
On budget: the tank is rarely the largest line. Filter, heater, light, timer, substrate, hardscape, plants, dechlorinator and a liquid test kit together usually cost more than the glass box. Then there is the running cost, which for a planted tank is mostly the heater and, in a British winter, not trivial. Plan the whole system, not the tank.
Choosing the tank
Here is the piece of advice that beginners most often ignore and most often later wish they had taken: buy the biggest tank your space, floor and budget genuinely allow. Small tanks are marketed as beginner tanks. They are not. They are harder.
The reason is dilution, and it is basic chemistry rather than folklore. The same absolute amount of waste — one uneaten meal, one dead snail — produces a concentration inversely proportional to the water volume. In 20 litres it is a crisis; in 120 litres it is a blip. The same applies to temperature: a large body of water has more thermal mass and drifts more slowly when the heater fails or the room gets cold. Larger tanks are more chemically and thermally stable for straightforward physical reasons, and stability is precisely what a beginner needs while they are still learning what the numbers mean.
Sixty litres is a reasonable practical floor for a first community tank. Ninety to 120 litres is a genuinely comfortable place to learn. Below about 40 litres you are in nano-tank territory, which is a legitimate speciality but a harsh classroom.
Shape matters too, and here the rule is footprint over height. A tank's gas exchange happens at the water surface, its plants grow on the base, and most fish swim horizontally rather than vertically. A wide, shallow tank with a big surface area gives you better oxygen exchange, more planting area, easier light penetration to the substrate and more useful swimming space than a tall narrow tank of identical volume. Tall tanks also make the light work much harder to reach the bottom, which pushes you towards higher-output lighting, which pushes you towards algae.
The kit — and what you can skip
Four things are genuinely non-negotiable: a filter, a heater, a light on a timer, and a liquid test kit. Everything else is optional at the start.
The filter is the single most useful thing to oversize. A filter's real job in a freshwater tank is not polishing the water — it is housing the bacteria that convert ammonia to nitrite and nitrite to nitrate, plus the ones that do the whole conversion in a single organism. Media volume is what determines how much of that population you can support, so a filter rated for a tank larger than yours buys you a bigger safety margin against overfeeding, a death you did not notice, or the day you add six more fish than you planned. Flow is a secondary consideration; in a planted tank you want gentle, well-distributed circulation rather than a torrent.
If you want the underlying biology, how nitrogen waste moves through an aquarium covers where ammonia actually comes from, the filter media guide explains what each type of media is for, and the comammox article covers the discovery that a single bacterium can do the whole ammonia-to-nitrate conversion — a genuine revision to the two-step textbook model that most aquarium advice still repeats.
The heater. Roughly 1 to 1.5 watts per litre is the practitioner rule of thumb, and it is a reasonable one: it is sized for the temperature difference between a typical room and a typical tropical tank. It is a convention rather than a derived constant, so treat it as a starting point and adjust for a cold room. Put the heater where there is flow so the warmed water actually circulates, and put a thermometer at the far end of the tank — the thermometer is how you find out the heater has failed, and heaters do fail.
The light. For a first planted tank, modest is safer than powerful. Light drives photosynthesis, and photosynthesis is limited by whatever runs out first — usually carbon or nutrients. Give plants more light than they can use and the surplus energy is available to algae instead. A moderate LED on a timer for six to eight hours a day is a good starting point, extended later if the plants clearly want it. How much light aquarium plants actually need gets into the measurements properly.
Established: light, carbon and nutrients co-limit plant growth, and photosynthesis in aquatic plants is very often carbon-limited in still water. Practitioner convention: the specific numbers the hobby uses — watts per litre, six to eight hours, “low light” thresholds — are useful rules of thumb derived from collective experience, not from controlled aquarium studies. Treat them as starting points, not constants.
What you can skip. CO2 injection is optional, and for a low-tech planted tank it is genuinely unnecessary. Plenty of plants — anubias, java fern, cryptocorynes, most mosses, hardy stems like hygrophila — grow perfectly well on the dissolved CO2 that arrives naturally from the air and from fish and bacterial respiration. They grow slowly, which is a feature when you are learning. You can also skip: a UV steriliser, an air pump (in a planted tank the plants themselves are a daytime oxygen source), a protein skimmer (that is a marine device), and almost every additive on the shop shelf other than dechlorinator.
Substrate & hardscape
Substrate is the first decision that is genuinely hard to change later, because changing it means taking the tank apart. There are two honest paths.
Enriched substrates — aquasoils and similar — carry nutrients and have a high cation exchange capacity, meaning they hold nutrient ions and release them to roots rather than letting them wash away. They genuinely help rooted plants establish. The trade-offs are real: they cost more, they often leach ammonia for the first few weeks (which is fine during a fishless cycle and a serious problem if fish are already in there), they soften and acidify the water, and they break down over a period of years. That buffering also quietly invalidates the standard KH-based CO2 calculation, which matters later if you go high-tech — the substrate and CEC guide covers the mechanism.
Inert substrates — sand, fine gravel — do nothing chemically. They are cheap, permanent and predictable, and plenty of beautiful planted tanks run on them, with root tabs pushed under the heavy root feeders and water-column dosing for the rest. If you want the lowest-drama option and do not mind slower initial establishment, this is it.
Depth and shape matter more than most people expect. Aim for around 3–4 cm at the front rising to 6–8 cm at the back. The slope is partly aesthetic — it exaggerates perspective and makes a small tank look deeper — and partly practical, since the tallest plants go at the back and need the most root room. Grain size should be fine enough for roots to grip but coarse enough not to compact; very fine sand in a deep bed with no movement is where anaerobic pockets form.
Hardscape — stone and wood — goes in dry, before water, and it should sit on the tank base rather than on top of the substrate so it cannot shift and slump later. Two compositional habits get beginners a long way: use odd numbers of stones with one clearly dominant piece rather than a symmetrical arrangement, and leave open space rather than filling every centimetre. Wood will usually float for weeks before it waterlogs, so plan to weight it down or wedge it under stone.
Build the entire layout dry and live with it for a day. Rebuilding a scape costs nothing before the water goes in and is thoroughly miserable afterwards. This is also when to check the tank is still level with the substrate load in it.
Water in, plants in
Fill slowly, onto something. Pour onto a plate, a bowl or a plastic bag laid over the substrate, or the first jug will excavate the scape you just spent an afternoon building. Treat the water with dechlorinator as you go: tap water in the UK is disinfected with chlorine or chloramine, both of which are acutely toxic to fish and to the bacteria you are about to try to cultivate. The chlorine and chloramine guide explains why chloramine in particular needs a product that handles the ammonia it releases.
Then plant. Immediately, and heavily.
Plant before fish, and plant more than looks necessary. A densely planted tank from day one starts consuming ammonium and nitrate straight away, occupies the nutrient niche that algae would otherwise take, and establishes far faster than a sparse one. Planting a third of what you eventually want and hoping it fills in is how you end up with an algae phase instead. Fast-growing stems are the workhorses here even if you eventually replace them — they do the early nutrient stripping while the slower, prettier species settle in.
New plants need preparation: remove rock wool and pots, trim damaged leaves and long roots, split bunches into individual stems and plant each one separately, and plant deep enough that they stay put. Preparing and planting new aquarium plants walks through it properly.
Then expect it to look worse before it looks better. Most aquarium plants are grown emersed — out of the water, in humid greenhouse conditions — and the leaves they arrive with are built for air, not water. Those leaves frequently dissolve within a fortnight while the plant grows an entirely new submersed set. This is plant melt, it is normal, and the correct response is to trim the mush away so it does not rot, and wait. Cryptocorynes are notorious for it. Pulling a melting plant out and returning it to the shop is the classic beginner error; it was working.
Cycling — the part everyone skips
This is the phase that separates tanks that thrive from tanks that limp. It is also the phase where nothing visible happens for weeks, which is exactly why it gets skipped.
Fish excrete ammonia, mostly across their gills, and uneaten food and waste decompose into more of it. Ammonia is acutely toxic. In a mature tank it never accumulates because two microbial populations consume it continuously: ammonia-oxidising organisms convert ammonia to nitrite, and nitrite-oxidising bacteria convert nitrite to nitrate. Nitrite is also acutely toxic. Nitrate is far less so, and it is what your water changes and your plants remove. (The textbook two-step picture is now known to be incomplete — complete ammonia oxidisers, or comammox bacteria, perform both steps in one organism and appear to be common in aquarium filters. The practical upshot for you is unchanged.)
In a brand-new tank those populations do not yet exist in useful numbers. Cycling is the process of growing them before anything is depending on them.
How to run a fishless cycle
Fishless cycling is the default recommendation here, for one straightforward reason: the alternative is using live fish as the ammonia source, which means deliberately exposing them to concentrations known to damage gill tissue and depress immune function. There is no welfare argument for it and no practical advantage.
The method: with the tank filled, planted, heated and the filter running, add a source of ammonia — unscented household ammonia with no surfactants, or a dedicated aquarium product — to reach roughly 2 ppm total ammonia. Then test. Every day or two, record ammonia, nitrite and nitrate.
You will see ammonia hold, then start falling as the ammonia oxidisers multiply. As it falls, nitrite appears and climbs — often to alarming levels, which is normal and expected with no fish present. Nitrite then falls in turn as the second population catches up, and nitrate accumulates. Re-dose ammonia back to about 2 ppm each time it reads zero, so the population you are growing does not starve.
The tank is cycled when a full dose of ammonia is processed to zero ammonia and zero nitrite within 24 hours. Not “ammonia is zero” on its own — that only proves the first half of the chain works. Both, from a full dose, in a day.
Typical duration is three to six weeks at tropical temperatures. It goes faster if you seed the filter with mature media, gravel or filter squeezings from an established healthy tank — that is transplanting the bacteria rather than growing them from scratch, and it is the single most effective accelerator. It goes slower in cooler water and at extreme pH. Bottled bacteria products vary enormously in whether they contain viable relevant organisms; some appear to help, many do less than the label implies, and the honest position is that the evidence is inconsistent. Treat them as a possible head start, never as a substitute for testing.
About “silent” or planted cycling
You will be told that a heavily planted tank can be stocked immediately because the plants handle the ammonia. There is a real mechanism underneath this, and it is routinely overstated.
The mechanism is genuine: aquatic plants take up ammonium directly as a nitrogen source, and many prefer it to nitrate because it is metabolically cheaper to assimilate. A dense mass of fast-growing plants really can intercept a meaningful fraction of the ammonia produced in a lightly stocked tank, which is why heavily planted tanks often show little or no measurable ammonia spike.
The overstatement is in what follows from that. Uptake capacity is finite and depends on how much healthy fast-growing plant mass you actually have, how much light and nutrients they have to work with, and how much waste is being produced. It is at its weakest in precisely the first few weeks, when new plants are melting and re-rooting rather than growing hard. Meanwhile an enriched substrate may be leaching ammonia of its own. And a planted tank that never accumulated ammonia has, by definition, never grown a large bacterial population — so its capacity to absorb a sudden increase in bioload is small.
Established science: aquatic plants assimilate ammonium directly and often preferentially. Reasonable inference: a heavily planted, lightly stocked tank can therefore keep ammonia below detection during establishment. Overstated hobby claim: that this makes cycling unnecessary, or removes the need to test. It does neither. Silent cycling is a legitimate approach for someone with dense mature planting and very light initial stocking — it is not a shortcut, and it does not exempt anyone from a test kit.
So: if you plant heavily and stock very lightly and test daily, a planted cycle can work. It is still a cycle. The test kit is what tells you which situation you are actually in, and the honest version of the advice is that it takes longer to be confident this way, not less time.
For more depth on what is actually happening in the filter while you wait, the filter maturity guide covers how long a biological filter really takes to reach full capacity, and the cloudy water article explains the bacterial bloom that often appears around week one and resolves on its own.
First fish
Do a large water change first — a cycled tank has a substantial nitrate load from weeks of ammonia dosing, and you want to start the stocked tank clean. Then add one small group. Not the full stocking list. One species, a proper shoal of six or more if it is a schooling fish, and then nothing else for two or three weeks.
The reason is that your bacterial population is sized to the ammonia you have been feeding it. Adding a full stocking list at once can outpace it, producing a small ammonia spike in a tank that was, on paper, cycled. Stocking in stages lets the population scale up with the load. Keep testing through the first fortnight; that is the period where a mistake is still recoverable.
Choose hardy, small, peaceful species for the first group — and choose ones suited to your actual tap water rather than fighting your water chemistry from day one. Check adult size and shoaling requirements before buying, not after; a great many stocking disasters are simply fish that grew.
Acclimatisation matters because the water in the bag is not your water. Temperature, pH and hardness can all differ, and pH in a sealed bag drifts as CO2 from the fish's respiration accumulates. Float the bag to equalise temperature, then introduce your water gradually over 20 to 40 minutes, and net the fish into the tank rather than pouring shop water in with them. The acclimatisation guide covers the trade-offs between the drip and float methods, including the argument that very slow acclimatisation can be worse when ammonia has built up in the bag.
Quarantine is the practice of keeping new fish in a separate simple tank for two to four weeks before they join the display. Being straight about it: most beginners will not do this, and most get away with it. It is best understood as risk management rather than a rule — the cost is a spare tank and some patience, and the thing it protects you against is introducing a pathogen or parasite into an established community, which is genuinely hard to undo. The more you have invested in the display tank, the better that trade looks. The quarantine science article and the fish disease guide set out what the evidence actually supports.
The first three months
The routine is short and it is the whole game. Once a week: a 25–40% water change with dechlorinated water at roughly tank temperature, a gentle substrate vacuum in open areas, a glass wipe, a plant trim, and a look at the numbers. Once a month: rinse filter media in old tank water, never under the tap, because chlorinated water kills the bacteria you spent six weeks growing. That is it.
Water changes do several things at once: they export nitrate and dissolved organics, replenish minerals the plants and fish consume, and dilute anything you have not thought to measure. The water changes guide covers what the evidence supports about frequency and volume.
Feed less than you think. Overfeeding is the most common single cause of water quality problems in new tanks. Everything that goes in and is not eaten becomes ammonia. A small amount once a day, consumed within a couple of minutes, is plenty.
Algae is normal. Almost every new tank goes through an algae phase somewhere in the first eight to twelve weeks, typically diatoms — a brown dust on glass and leaves — followed by whatever else finds a niche. A new tank has not yet settled into a stable balance between light, nutrients and plant growth, and algae colonise the gap. It generally resolves as the plants take hold. The productive responses are to keep the light period modest and fixed, keep up water changes, keep the plants growing, and wait. The unproductive response is to start dosing algae treatments at a tank that is simply young.
If the water goes cloudy in the first week or two, that is usually a bacterial bloom rather than a problem — clear water is not itself a health test, and the bloom typically clears on its own once the microbial community stabilises.
What normal actually looks like at this stage: 0 ppm ammonia, 0 ppm nitrite, nitrate somewhere in the low tens and falling after each water change, stable temperature, fish eating and colouring up, new leaves appearing on the plants, and some algae you are learning to ignore. If ammonia or nitrite is ever detectable in a stocked tank, that is the one situation that needs immediate action: a large water change, and stop feeding for a day or two.
Four tools you will actually use
These are parallel — reach for whichever one the current question needs. All of them are free and none of them need an account.
Tank volume
The real water volume after fill level and substrate — the number every dose and calculation depends on.
Open the calculator → HardwareSubstrate
Litres, weight and bags for your footprint and your front-to-back depth, before you get to the shop.
Open the calculator → SpeciesPlant & fish lookup
Light, CO2 and difficulty for plants; water chemistry, adult size and temperament for fish.
Browse the species → TrackingParameter log
Record the cycle day by day and keep logging afterwards. Trends tell you far more than single readings.
Start logging →What good looks like at six months
At six months a well-run first tank is unrecognisable from the one you filled. The plants have grown into each other and you are trimming rather than waiting. The substrate is no longer visible in the planted areas. Ammonia and nitrite have read zero for so long that you have stopped testing them weekly. Nitrate sits in a predictable band and drops after each water change. The algae phase came, did its thing, and receded to a film on the glass that you wipe on a Sunday.
The fish look different too. Settled fish colour up, shoal loosely rather than nervously, and behave like animals that are not braced for something. Some of them will have started breeding without being asked, which is the clearest signal you will get that the tank is genuinely healthy.
And the routine has shrunk. Twenty minutes on a Sunday, a glance at the tank each evening, a bag of fertiliser every few months. The tank is no longer a project. That is the actual goal of everything above: not a perfect tank, but a stable one that does not need you to be vigilant.
The other thing that tends to happen around month six is that you start getting curious. Why does the pH read differently in the morning? What would happen with more light? What are these people doing to grow a carpet like that? That is the point where this stops being a setup exercise and becomes the hobby proper.
When that happens, the companion piece to this one is The art & science of the planted aquarium — how aquascaping became an art form, what the different styles are actually doing, and the water chemistry underneath all of it. This page is how you get a tank. That one is why you will not stop at one.
Two last honest notes. First, everything here has a range rather than a number, because tanks differ — your water, your room temperature, your plants and your stocking all move the timings. Treat every figure on this page as a starting point that your own test kit corrects. Second, you will make mistakes, and almost none of them are fatal if you are testing and doing water changes. The people with beautiful tanks are not the ones who never got it wrong. They are the ones who kept the routine going while they worked it out.