Most first fish tanks fail within six months. Not because the hobby is hard, but because nobody explains the setup properly and shops sell equipment in the wrong order. This guide is the honest, UK-first version of what to do — from buying the tank to adding the first fish — that gives your fish the best chance of thriving.

Set aside a weekend for the physical setup, plus 4–6 weeks for the tank to cycle before adding fish. Yes, six weeks. This is not negotiable. More on that in step 6.

The kit list

Everything you need for a 60–100 litre tropical community tank (the ideal beginner size), in UK 2026 prices.

Essential:

• Tank + stand: 60L Fluval Flex kit or Juwel Primo 70 or a bare tank + aquarium stand rated for 100kg+. £70–£180.
• Filter: Fluval U2 internal for tanks under 60L, Fluval 107 external canister for 60L+. £25–£85. See our filter roundup for detail.
• Heater: 50W adjustable heater for 30L, 100W for 60L, 200W for 120L+. Always adjustable and thermostat-controlled, never a plain “10W” heater. £15–£40.
• Thermometer: Digital aquarium thermometer. Stick-on strips are unreliable. £5–£10.
• Substrate: Aquarium sand or natural gravel. 1kg per 4L of tank. £15–£30.
• Dechlorinator: Seachem Prime. Small bottle lasts a year. £10.
• Test kit: API Freshwater Master Test Kit. The essential kit for cycling and ongoing water quality. £25–£30.
• Bottle of pure household ammonia (for fishless cycling — see step 6). About £3 from the cleaning aisle.

Nearly-essential:

• LED lighting (if not built into the tank kit): aquarium LED bar. £15–£40.
• Plug timer for the light. £5.
• Bucket dedicated to aquarium use (never used for detergents).
• Gravel vacuum: aquarium gravel vacuum with hand pump. £10.
• Fish net — one big and one small.

Nice to have:

• Aquarium bogwood or spider wood — £15–£30
• Live plants (see step 5)
• Indian almond leaves — £5–£10
• Backing paper (behind the tank, hides cables)

Total starter budget: £180–£350 depending on tank size and how much you buy new vs used.

Step 1 — Choose the location

The single most important decision. Once you fill the tank, you cannot easily move it.

Requirements:

• Level, sturdy floor. A full 100-litre tank + stand weighs 130+ kg. Test with your foot on the exact spot — if the floor gives at all, you need a different location.
• Not in direct sunlight. Windows facing south or west guarantee green algae blooms within weeks. North-facing or interior walls are best.
• Away from heaters, radiators, or draughts — inconsistent room temperature stresses the heater and the fish.
• Near a power socket but not with cables trailing where they’ll get wet.
• NOT on a wardrobe, chest of drawers, or bookshelf unless the manufacturer explicitly certifies the load. Furniture rated for clothes is not rated for 130 kg of water.
• Not in a busy walkway where people constantly walk past — fish stressed by movement will hide constantly.
• Where you can see it from where you spend time. The whole point is to enjoy the tank.

Step 2 — Set up the stand and rinse the substrate

Place stand in its final location. Level it — a small builder’s spirit level shows a lot. If it wobbles, shim under one corner with a folded piece of card. An unlevel tank puts stress on the glass and can crack.

Wash the substrate before adding to the tank:

• Sand: rinse in a bucket, agitate vigorously, drain, repeat until the drained water is clear. This takes 10+ rinses for silver sand. Skip this step and you’ll have cloudy water for weeks.
• Gravel: rinse until water runs clear. 5+ rinses usually enough.

Add substrate to the empty tank on the stand. Aim for 3–5 cm depth minimum for gravel, 4–6 cm for sand (deeper substrate hosts more beneficial bacteria).

Step 3 — Add hardscape and equipment

Hardscape (wood, rocks) goes in before water. It’s much easier to arrange when you can move things freely.

• Pre-soak new wood for a week in a bucket to release excess tannins and help it sink.
• Rocks: only aquarium-safe rocks. Random rocks from a garden may leach minerals and change your water chemistry. Slate and dragon stone are safe UK-available options.

Install equipment:

• Heater — attach to back or side wall with suction cups. Do NOT plug in yet; running dry burns them out immediately.
• Filter — internal filter goes at the back or in a corner. External canister goes under or beside the tank with intake and outlet in place. Again, do NOT plug in yet.
• Thermometer — opposite end of the tank from the heater, so you’re measuring the coldest point.

Step 4 — Fill the tank

Use lukewarm tap water — cold water shocks glass, hot water damages silicone seals over time. Add water slowly so you don’t stir up the substrate; a small plate placed on the substrate and pouring water onto that helps.

Fill to about 1 cm below the top rim.

Dechlorinate immediately — dose Seachem Prime for the full tank volume (5 ml per 200 L). UK tap water always contains chlorine or chloramine which kills fish and beneficial bacteria.

Now plug in the heater, filter, and lights. Set the heater to 26 °C and leave for 24 hours to stabilise.

Step 5 — Add live plants (before fish)

Plants stabilise the tank chemistry, absorb ammonia during cycling, and improve every measure of tank health. Add them BEFORE cycling starts if you can.

Beginner-safe plants for UK tap water:

• Java fern — attaches to wood, no substrate needed
• Anubias — same, low-light tolerant
• Vallisneria — root plant, background tall grass
• Cryptocoryne — root plant, mid-ground
• Java moss — grows on anything, hides fry, low-maintenance

Buy from an independent aquatic shop where possible; big-box store plants are often marsh-grown emersed plants that die within weeks.

Step 6 — Cycle the tank (4–6 weeks)

This step is where 90% of first-tank failures happen. Do not skip.

Cycling means growing the beneficial bacteria that convert toxic fish waste (ammonia) into nitrite, then nitrate. Without cycling, adding fish immediately means they swim in slowly-poisoning water.

Fishless cycle (recommended):

1. Add pure household ammonia to the tank until the API test kit reads 3–4 ppm ammonia.
2. Wait, test daily. After 5–14 days, ammonia will drop as bacteria colonise.
3. Nitrite will rise as ammonia falls. This is normal.
4. Continue dosing ammonia to maintain 2–4 ppm daily.
5. After another 2–4 weeks, nitrite will crash to 0 and nitrate will start reading.
6. When you dose a fresh dose of ammonia and it processes to 0 within 24 hours, the tank is cycled.

Full protocol in our UK cycling guide.

Do not use “cycling accelerator” bottled bacteria as a substitute for waiting. They speed the process by maybe a week, not eliminate it.

Step 7 — Add the first fish (slowly)

Cycled tank, stable temperature at 26 °C, all readings zero except a low nitrate? Now you can shop for fish.

Choose species first before buying:

• Read our best fish for UK beginners guide — hardy species suited to your tank size.
• Compatible tank mates. Check species-to-species (see our species-profile pages).
• Adult sizes. A “small fish” in the shop might grow to 15cm.

Buy from a good source:

• Independent aquatic shops with visibly healthy stock (all fish alert, no dead fish visible)
• Avoid: any shop where you spot obvious disease in ANY tank; their whole system may be contaminated.

Introduce in small groups over weeks:

• Week 1: 4–6 hardy fish (danios, hardy tetras, small livebearers)
• Wait 2 weeks. Test daily. Any ammonia spike → wait, water change.
• Week 3: another 4–6 fish
• Continue at 2-week intervals until you’re at target stocking.

Never do “the whole community at once” — even a cycled tank can’t handle a doubling of bioload overnight.

Step 8 — Establish a maintenance routine

The routine that keeps a UK community tank healthy:

Weekly:

• 25% water change with dechlorinated water at matching temperature.
• Test ammonia, nitrite, nitrate. All should be 0/0/<40.
• Wipe front and side glass clean with a plain algae magnet or aquarium magnet cleaner.
• Vacuum any visible waste from the substrate.

Monthly:

• Rinse filter media in bucket of removed tank water (NEVER tap water — chlorine kills bacteria).
• Trim/replant plants as needed.
• Clean the outside of the glass.

Daily:

• Feed once or twice, only what fish clear in 2 minutes.
• Visual check for sick fish, missing fish, or unusual behaviour.
• Note water temperature.

Common mistakes to avoid

• Adding fish immediately. Kills fish, launches you into weeks of cycling with fish suffering in the tank. Wait.
• Overfeeding. The single biggest source of ongoing water quality issues.
• Overstocking. “One inch per gallon” is misleading — waste production scales with fish size and messiness (goldfish and plecs are far more polluting per cm than tetras).
• Rinsing filter media in tap water. Chlorine kills bacterial colony overnight — the tank effectively un-cycles.
• Buying fish that grow too big. Common plecos reach 45cm. Tinfoil barbs reach 35cm. Silver dollars reach 15cm. Ask adult size before buying.
• Chasing “perfect” pH. Stability matters more than the specific number. Fiddling with pH usually makes things worse. See our pH guide.

Bottom line

Two hours of physical setup. Six weeks of patience while cycling. Then decades of enjoyment (bristlenose plecs live 10 years, kuhli loaches 10+, zebra danios 5, bettas 4). Skip the cycling and you’ll be starting over with dead fish and disillusion within months.

The whole hobby rewards taking the time.

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Next steps: cycle your tank properly, then pick beginner-safe UK fish. Working out how many fish fit in your tank? Use the volume calculator.

— Jaqline Smalling, FishForever