Getting Started with Aquarism

Why aquarism is worth your patience

Aquarism is the practice of keeping fish, plants, and other aquatic life in a home aquarium. At its best, it isn’t a fish in a bowl — it’s a small, living ecosystem you design, build, and learn to read. Watching a tank you cycled yourself settle into balance is one of the most quietly satisfying experiences a hobby can offer.

It’s also a hobby where the single most important skill is patience. Almost every beginner disaster — dead fish in week one, runaway algae, endless cloudy water — traces back to rushing a step that wanted two more weeks. The good news: if you can wait, the hobby is remarkably forgiving and inexpensive to do well.

This guide walks the whole journey in order: planning your tank, choosing equipment, setting it up, cycling it (the step most beginners skip, and shouldn’t), choosing your first fish, feeding, and the simple weekly routine that keeps everything alive. The deep dives at the end cover species recommendations, plants, algae, diseases, and what changes if you go saltwater.

One honest expectation to set now: your tank will not be ready for fish on day one. Between setup and your first fish there’s a 3–6 week biological process called the nitrogen cycle. Knowing that in advance is what separates keepers whose first fish thrive from those who restart three times.

Planning your first tank

The decisions you make before buying anything determine 80% of how smooth your first year goes.

Bigger is easier, not harder

Counter-intuitively, small tanks are the hard mode of this hobby. Water dilutes mistakes: in a 100-litre tank, a missed water change or a bit of overfeeding moves your water chemistry slowly; in a 20-litre tank the same mistake can spike ammonia overnight. Aim for at least 40 litres, and if budget and space allow, 75–150 litres is the beginner sweet spot — more forgiving, and more stocking options.

Where to put it

• Out of direct sunlight — sunlight is the fastest route to algae problems.
• Away from drafts, radiators, and AC vents — temperature swings stress fish and make your heater work erratically.
• On a surface that can take the weight — water weighs 1 kg per litre before you add glass, substrate, and rock. A filled 100-litre setup approaches 150 kg.
• Near a power outlet, and somewhere you’ll actually sit and watch it.

Freshwater or saltwater?

Freshwater is the recommended start: equipment is simpler, hardy species abound, and mistakes are cheaper. A planted freshwater tank is genuinely beautiful and low-maintenance once established.

Saltwater delivers the reef-tank drama — but costs roughly 3–5× more to start (≈ €500–700 for fish-only, double for reef), demands tighter parameter control, and adds daily chores like evaporation top-off. It’s absolutely achievable, but most keepers are happier doing a year of freshwater first. The saltwater deep dive covers exactly what changes.

A realistic starting budget (freshwater)

Fish come later — and that’s a feature, not a bug, as the next sections explain.

Equipment, explained

You need less gear than the pet store implies — but the gear you do need has a job worth understanding.

The filter: a home for bacteria, not just a sieve

A filter does three things: mechanical filtration (trapping debris), chemical (optional carbon to remove discolouration), and — the one that actually keeps fish alive — biological: housing the colonies of nitrifying bacteria that convert toxic fish waste into safer compounds. When keepers say “the filter is the heart of the tank”, they mean the bacteria living in it.

Pick a filter rated at or above your tank size. You can’t meaningfully over-filter a tank, but you can under-filter one.

Heater and thermometer

Tropical fish need a stable 24–27 °C. Rule of thumb: about 1 watt per litre, more if the room runs 5 °C or more below your target. For tanks over ~200 litres, two smaller heaters beat one large one — if a heater fails stuck-on or stuck-off, the damage is halved. Always run a separate thermometer; heater thermostats drift, and a €3 thermometer is the cheapest insurance in the hobby.

Test kit: liquid over strips

You cannot see ammonia. The only way to know what’s happening in your water is to test it. Liquid test kits are significantly more accurate than paper strips, which are hard to read and degrade within months of opening. Strips are fine as a quick mid-week check, but own a liquid kit covering at minimum: ammonia, nitrite, nitrate, and pH. Log every reading — trends matter more than single numbers, and that’s exactly what AquaKeepers is built for.

The rest

• Lighting — any decent LED works for fish; plants need adequate output (see the planted deep dive). Put it on a timer: 6–8 hours daily.
• Water conditioner — neutralises chlorine and chloramine in tap water. Non-negotiable; untreated tap water kills your filter bacteria and burns fish gills.
• Substrate — gravel or sand. Fine sand if you want corydoras (they sift it with delicate barbels).
• Bucket + siphon — dedicated to the aquarium only, never used with detergents.

What you don’t need yet

CO₂ systems, UV sterilisers, dosing pumps, wavemakers, “complete” chemical kits that promise to skip the cycle. Beginners are sold a lot of gear that solves problems they don’t have.

Setting up, step by step

Setup day is satisfying — and ends with an empty-of-fish tank, on purpose.

1. Rinse the substrate in a clean bucket until the water runs clear. Skipping this guarantees days of cloudy water.
2. Place hardscape (rocks, wood) directly on the glass or deep in the substrate so later digging can’t topple it. Slope the substrate slightly toward the front — debris collects where you can see and siphon it.
3. Fill slowly — pour onto a plate or bag laid on the substrate to keep it from clouding.
4. Dechlorinate — dose water conditioner for the full tank volume.
5. Install filter and heater, wait 20 minutes for the heater’s glass to acclimate, then power everything on.
6. Run it for 24 hours. Check: is the temperature stable at 24–27 °C? Is the filter flowing quietly? Any leaks?

If you’re planting live plants, plant them now — they help the tank mature (and the planted deep dive lists species that survive beginners).

What’s normal in week one

• Milky/cloudy water after a day or two is a bacterial bloom. It clears by itself; don’t chase it with chemicals or water changes.
• A brown dusty film appearing in the first weeks is diatom algae — a rite of passage for new tanks that fades as the tank matures (see algae control).

Your tank now looks done. Biologically, it’s a sterile box — the next section is the most important one in this guide.

The nitrogen cycle: the step that keeps fish alive

If you read one section of this guide, make it this one. “New tank syndrome” — adding fish to an uncycled tank — is the single most common reason beginner fish die.

The problem

Fish excrete ammonia (NH₃), and so does decomposing food. Ammonia is toxic at any detectable level. In nature it disperses; in a glass box it accumulates — unless something removes it.

The solution is bacteria

Two groups of nitrifying bacteria colonise your filter and surfaces:

Ammonia (toxic) → Nitrosomonas → Nitrite (NO₂⁻, also toxic) → Nitrospira → Nitrate (NO₃⁻, low toxicity)

Nitrate is removed by your weekly water changes and consumed by plants. “Cycling” a tank means growing these bacterial colonies before any fish depend on them. They take weeks to establish — there is no instant shortcut, though there are accelerators.

Fishless cycling, step by step

1. With the tank running (filter on, heater at ~26 °C), add bottled ammonia (unscented, no surfactants) or a dedicated cycling ammonia product to reach 2–4 ppm on your test kit.
2. Test ammonia and nitrite every day or two. First you’ll see ammonia fall and nitrite spike — the first bacteria are working. Then nitrite falls as the second group establishes.
3. When ammonia drops below ~1 ppm, re-dose back to 2 ppm. Don’t dose daily on a schedule — overdosing spikes nitrite so high it stalls the cycle.
4. You’re cycled when: you dose 2 ppm of ammonia, and 24 hours later both ammonia and nitrite read 0. Nitrate will be high — that’s the proof the chain works.
5. Do a large water change (50%+) to bring nitrate down, match the temperature, and you’re ready for your first fish.

How long?

Typically 3–6 weeks from scratch. Two genuine accelerators: bottled nitrifying bacteria (can shorten the process to 1–2 weeks) and — best of all — seeded media: a piece of mature filter sponge from a healthy established tank brings the colony with it.

Track it

A cycling log is the perfect first use of AquaKeepers: log ammonia, nitrite, and nitrate every test, and you’ll literally watch the two bacterial populations rise as curves on a chart — and know, rather than guess, the day your tank is safe for fish.

First fish, done right

The tank is cycled. Now the part you’ve been waiting for — slowly.

Forget “one centimetre of fish per litre”

The old inch-per-gallon rule survives because it’s simple, not because it works. A fish twice as long has roughly eight times the mass and waste output, and the rule says nothing about behaviour, territory, or swimming space. Think instead about:

• Adult size — that 3 cm pleco in the shop can become a 30 cm problem. Always look up the adult size before buying.
• Bioload — how much waste the species produces relative to your filter.
• Behaviour — schooling fish need groups of at least 6 of their own species; in smaller groups they live in chronic, health-shortening stress. Territorial fish need layout and space.
• Compatibility — match temperament, water preferences, and adult sizes. Research every species against every other; the species guide lists proven beginner combinations.

Stock slowly

Your bacteria colony is sized for the waste it currently receives. Add a few fish at a time, 1–2 weeks apart, testing ammonia and nitrite in between. A fully stocked tank reached over two months will be healthier than the same tank stocked in one afternoon.

Acclimatise every new fish

1. Float the sealed bag in the tank for 15–20 minutes to equalise temperature.
2. Open the bag and transfer fish and bag water into a bucket below tank level.
3. Run a siphon of tank water through airline tubing at 2–4 drips per second until the bucket’s volume roughly doubles (30–60 minutes).
4. Net the fish into the tank. Discard the bucket water — never pour shop water into your aquarium.

For hardy freshwater species, floating the bag and adding small cups of tank water every 10 minutes is an acceptable simpler version. For sensitive species and all invertebrates, drip.

New fish hide, school tightly, and refuse food on day one. That’s normal; judge them on day three.

Feeding without polluting

Here’s the uncomfortable truth: far more aquarium fish are killed by overfeeding than by underfeeding — not directly, but through what uneaten food becomes: ammonia.

How much, how often

• Feed once or twice a day, only what’s fully eaten in 2–3 minutes. If food is hitting the substrate untouched, you fed too much.
• A weekly fasting day is harmless and mirrors how most species live in nature.
• Vary the diet: a quality flake or pellet as the staple, plus frozen or live food (bloodworms, brine shrimp, daphnia) once or twice a week, and blanched vegetables for grazers like otocinclus.
• Sinking food for bottom-dwellers like corydoras — they shouldn’t depend on leftovers.

Chronic overfeeding hurts twice: it degrades water quality, and it causes fatty liver disease and constipation in the fish themselves. A slightly hungry tank is a healthy, active, algae-grazing tank.

Holidays

Healthy adult fish are completely fine up to a week without food. For a weekend trip: do nothing — that’s safer than any alternative. For longer absences, use an automatic feeder (run it for a week before you leave to dial in portions), or leave pre-portioned doses for a helper — never the container, helpfulness scales into overfeeding. Avoid dissolving “vacation blocks”; they mostly feed your ammonia readings.

And don’t “feed them up” before leaving — a big meal the day you walk out the door is the worst-timed water-quality bomb you can set.

The routine that keeps it alive

A thriving tank runs on a boring, 30-minute weekly ritual. Consistency beats intensity: four small water changes a month do far more good than one heroic deep clean.

The weekly water change

Change about 25% of the water every week (10–30% depending on stocking — heavily stocked or messy fish, more; lightly stocked planted tanks, less).

1. Scrape glass if needed; gravel-vacuum a different patch of substrate each week while draining into a bucket.
2. Refill with conditioned tap water, roughly temperature-matched (±2 °C).
3. Test and log your parameters — same day each week, so trends are comparable.

Filter care — the two golden rules

1. Never rinse filter media under tap water. Chlorine kills the bacteria colony you spent six weeks growing. Swish mechanical sponge in the bucket of water you just removed from the tank, every 2–4 weeks.
2. Never replace all media at once, no matter what the cartridge packaging says. Replace at most half at a time, weeks apart, so the colony persists. A grungy-looking biological sponge is a healthy one.

Your targets

The cadence

• Daily (2 min): feed, count fish, glance at temperature and filter flow.
• Weekly (30 min): water change, glass clean, test and log.
• Monthly: rinse mechanical media in tank water, trim plants, review the month’s trends.

This is exactly the loop AquaKeepers automates: recurring maintenance tasks with next-due dates, parameter logging, and a health score that turns “I think it’s fine” into a number you can trust. Create your tank and log your first reading — it’s free.