Fish & Aquariums

How to Take Care of a Fish Tank for Beginners UK

Q: What temperature should a beginner tropical tank be?

Aim for 24 to 26 degrees Celsius and keep it steady. Use a heater sized at roughly 5 watts per litre and check the thermometer daily. Coldwater fish like goldfish do not need a heater.

By Mark Whitfield · August 22, 2026

Taking care of a fish tank comes down to four habits: feed a small pinch twice a day, change 25 to 30 percent of the water every week, test the water once a week, and leave your filter bacteria alone. If you do those four things consistently, most beginner problems never appear, and the weekly routine takes about 10 minutes once you have the routine down.

This guide walks through exactly what to do each day and each week, what equipment actually helps in the UK, and the mistakes that trip up most first-time fishkeepers. You don't need expensive gear to keep fish healthy, you just need consistency.

1. The Daily Two-Minute Check

Every morning, take a quick look before you feed. Check that the filter is running and water is circulating, the heater light is on if you keep tropical fish, and the temperature reads 24 to 26°C on your thermometer. Then look at the fish for 30 seconds: are they swimming normally, eating eagerly, and showing no white spots, clamped fins or hovering at the surface gasping?

Those visual checks catch most problems early. A filter that has stopped, a heater that has stuck on, or a fish that has started hiding are all easier to fix on day one than on day five. If everything looks normal, feed a small pinch and you are done.

2. Weekly Water Change: The One Job That Matters Most

If you do nothing else, do the weekly water change. In a closed tank, fish waste breaks down into ammonia and then nitrate, and nitrate only leaves through water changes and live plants. Let nitrate climb and fish get stressed, algae explodes, and water goes cloudy.

Once a week, turn off the heater and filter, then siphon out 25 to 30 percent of the water with a gravel vacuum. Push the vacuum into the substrate to lift uneaten food and waste as you go. Refill with tap water that you have treated with a water conditioner first. UK tap water contains chloramine, which does not evaporate by sitting out, so a conditioner is essential every time.

Seachem Prime is the conditioner most UK fishkeepers keep on hand because it neutralises chlorine and chloramine and also temporarily detoxifies any ammonia and nitrite if your tank has a small spike. A 100 ml bottle treats 1,000 litres, so one bottle lasts months on a small tank. For a simpler dechlorinator, API Tap Water Conditioner does the chlorine and chloramine job cleanly. Treat the new water in the bucket before you pour it back in, match the temperature roughly by feel, then switch the heater and filter back on.

UK tip: If your area has very hard water (much of the South East and Midlands) and you keep soft-water species like neon tetras, ask your local shop what they keep their fish in. Keeping fish that suit your tap water is far easier than constantly trying to change the water chemistry.

3. Test Your Water Once a Week

You cannot see ammonia or nitrite, but your fish feel them at very low levels. A weekly liquid test tells you whether your filter bacteria are coping. You are looking for ammonia 0 ppm, nitrite 0 ppm, and nitrate under 40 ppm. If ammonia or nitrite show above zero, do an extra 30 percent water change and cut feeding for a day.

The API Freshwater Master Test Kit is the standard liquid kit we compare for beginners because it covers ammonia, nitrite, nitrate and pH with enough reagent for about 800 tests. That works out far cheaper per test than strips, and the colour readings are easier to distinguish at the low levels that actually matter during the first few months.

Test on the same day each week, before the water change, and jot the numbers down. After a few weeks you will see your tank's normal pattern, which makes any drift obvious.

4. Feed Less Than You Think

Overfeeding is the most common beginner mistake and the fastest way to dirty a tank. Fish will eat until they look bloated if you let them, and uneaten food sinks, rots, and feeds an ammonia spike. The rule we use is a pinch per fish, twice a day, and a single fasting day each week so their digestion can catch up.

Good food makes a noticeable difference. TetraMin Tropical Flakes are the balanced staple most community fish do well on, they soften quickly so small mouths can manage them, and they keep well if you store the pot sealed in a cool dry place. Feed them as the base, then vary with a small amount of frozen or pellet food once or twice a week if you have room in your routine. Whatever you buy, replace the pot every few months once opened, as stale food loses nutrients.

5. Keep Temperature Steady

Tropical community fish do best at a steady 24 to 26°C, and a UK living room swings more than that between a sunny afternoon and a cold night. A submersible heater set to the right temperature smooths those swings out. The rough guide is 5 watts per litre, so a 54-litre starter tank wants around a 100W heater, and a 200-litre tank wants a 200W unit.

The Interpet Deltatherm 50W Heater is a neat fit for nano and small tanks under 30 litres, with a simple temperature dial and a guard that helps prevent fish burning themselves on the glass. For anything over 50 litres, the Superfish Pro Heater 200W holds temperature accurately and switches off if the water level drops, which protects both the heater and your fish. Goldfish and other coldwater species are the exception: they do best without a heater at all.

Check the thermometer daily and the heater setting weekly. If the room gets very warm in summer, a small clip-on fan across the water surface can drop the temperature a degree or two through evaporation.

6. Leave Your Filter Bacteria Alone

Most of your beneficial bacteria live in the filter media, not in the water itself. The best way to keep them alive is to avoid cleaning the filter too much or too thoroughly. When flow drops or the sponge looks clogged, rinse the media gently in a bucket of old tank water you just siphoned out, then put it straight back. Never rinse filter sponges under hot tap water, and never replace all the media at once, as UK tap water chloramine will kill the colony you spent weeks growing.

Good starter filters give bacteria plenty of surface area. The Fluval U2 Internal Filter is a quiet internal option for 45 to 110 litre tanks with a large sponge block, and the AquaClear 50 Power Filter is a hang-on design with a big media basket that many UK beginners use on 75 to 190 litre setups because it is easy to customise and clean.

7. Light, Algae and a Quick Clean

Algae is normal, and a little on the glass is a sign of a healthy tank. Too much comes from too much light or too many nutrients. Keep the tank light on for 6 to 8 hours a day on a timer, keep the tank out of direct sunlight, and keep up with the weekly water changes. When algae builds up, wipe the inside glass with an algae scraper before the water change so the siphon can remove the loosened particles.

Live plants help by competing with algae for nutrients, but they are optional for your first tank. If you do add them, start with easy species like java fern or anubias that do well in UK tap water without injected carbon dioxide.

Products mentioned in this guide

API Freshwater Master Test Kit - liquid tests for ammonia, nitrite, nitrate and pH
Seachem Prime - water conditioner that also detoxifies ammonia and nitrite
Tetra Starter Tropical Aquarium 54L - sensible 54-litre starter tank for beginners
Interpet Deltatherm 50W Heater - compact heater for nano and small tanks
TetraMin Tropical Flakes - balanced staple flake food
Fluval U2 Internal Filter and AquaClear 50 Power Filter - filter options compared for UK beginners

FAQ

How often should beginners change fish tank water?

Change 25 to 30 percent once a week. That keeps nitrate under control without shocking the fish. If ammonia or nitrite ever read above zero, do an extra 30 percent change and test again the next day.

How often should I feed fish in a new tank?

Twice a day, a small pinch that fish finish in about one minute, plus one fasting day per week. Uneaten food should never sit on the bottom. If it does, you fed too much.

Do I need to test the water if the tank looks clear?

Yes. Clear water can still contain toxic ammonia or nitrite. A weekly liquid test is the only reliable way to know your biological filter is working. Test before the water change so the reading reflects the real weekly load.

What temperature should a beginner tropical tank be?

Aim for 24 to 26°C and keep it steady. Use a heater sized at roughly 5 watts per litre and check the thermometer daily. Coldwater fish like goldfish do not need a heater.

Can I change the filter sponge or rinse it under the tap?

Do not rinse filter media under tap water and do not replace it all at once. UK tap water chloramine kills the beneficial bacteria living in the sponge. Rinse gently in old tank water instead and replace media in stages if the manufacturer recommends it.

How long should the tank light stay on?

Six to eight hours a day on a timer is enough. More light grows more algae without helping the fish. Keep the tank out of direct sunlight as well.

Final Verdict

Taking care of a fish tank is less about buying the right gadget and more about repeating a few simple habits. Feed lightly, change the water every week with properly conditioned tap water, test once a week with a liquid kit like the API Freshwater Master Test Kit, keep temperature steady with a reliable heater, and leave your filter bacteria alone.

If you are starting from scratch, a 54-litre setup such as the Tetra Starter Tropical Aquarium 54L paired with Seachem Prime and a basic gravel vacuum covers the essentials for well under £120, then add fish slowly once the tank is cycled. That steady routine is what keeps water clear, fish active, and maintenance short week after week.