5 Steps to Keep Your Fish Tank Clean

1. Do a Partial Water Change Every Week

Replace 25-30% of your tank water once a week using a gravel vacuum. This removes dissolved waste, nitrates, and debris that your filter can't catch. Never do a full water change unless you're dealing with a disease outbreak, because it strips out the beneficial bacteria your tank depends on.

Use a python-style gravel vacuum to siphon water out while simultaneously cleaning the substrate. Work in sections across the tank floor, pushing the vacuum into the gravel to pull up trapped waste. For a 60-litre tank, this takes roughly 10-15 minutes.

Always match the temperature of the replacement water to your tank water within a couple of degrees. Fill a bucket, float it in the tank for a few minutes, or use a thermometer. Sudden temperature swings stress fish and can trigger illness.

2. Condition Your Tap Water Before Adding It

UK mains water contains chlorine or chloramine to keep it safe for human drinking. Both are lethal to fish and destroy the beneficial bacteria in your filter and substrate. Every drop of new water must be treated before it goes into the tank.

AQUARIAN Tap Water Safe is a straightforward option: add the recommended dose to your replacement water, stir, and it neutralises chlorine and chloramine within minutes. API Stress Coat goes further by also adding a protective slime coat supplement, which helps fish recover from minor injuries or netting stress. AquaCare Tap Water Conditioner is a budget-friendly alternative that handles the basics well.

Dosing matters. Follow the bottle instructions for your water volume. Under-dosing leaves chlorine in the water; over-dosing wastes product. For most conditioners, one capful treats 50-100 litres.

3. Clean Your Filter Media Without Killing Bacteria

Your filter is home to millions of beneficial bacteria that convert toxic ammonia into less harmful nitrates. Cleaning it wrong is the most common beginner mistake. The rule is simple: never replace all your filter media at once, and never rinse it under tap water.

Once a month, take out the filter sponge or media basket and squeeze it gently in a bucket of old tank water (the water you siphoned out during your water change). This loosens debris without killing the bacteria colony. If the water runs reasonably clear, put it back.

Replace carbon cartridges or ceramic rings on a staggered schedule, roughly every 6-8 weeks, replacing only a third of the media at a time. This keeps the bacterial colony stable while maintaining filtration efficiency.

4. Scrub Algae off Glass and Decorations

Algae buildup on glass is mostly cosmetic, but thick growth blocks light and looks unsightly. Use a magnetic algae cleaner or a razor-blade scraper on the inside of the glass during your weekly water change. Work from top to bottom, and avoid scraping near silicone seals.

For decorations, rocks, and driftwood, remove them during your water change and scrub them with a clean toothbrush under old tank water. Rinse them in dechlorinated water before putting them back. Don't use soap or chemicals, because residue can leach into the water.

Algae is often a symptom of too much light or too many nutrients. If algae is growing faster than you can clean it, reduce your lighting period to 6-8 hours per day and check you're not overfeeding your fish.

5. Test Your Water Monthly

A simple water test kit catches problems before they become emergencies. Test for ammonia, nitrite, nitrate, and pH once a month. In a cycled, healthy tank, ammonia and nitrite should read 0ppm, nitrate should be below 40ppm, and pH should be stable.

If ammonia or nitrite appear above 0ppm, something has disrupted your cycle. Common causes include overfeeding, a dead fish hidden in the tank, or cleaning filter media under tap water. Do a 50% water change immediately and test again the next day.

Liquid test kits like the API Freshwater Master Test Kit are more accurate than test strips and give better value long-term. A single kit lasts months for most hobbyists.

Products Mentioned in This Guide

• AQUARIAN Tap Water Safe 118ml - reliable chlorine and chloramine neutraliser for UK tap water
• API Stress Coat 473ml - water conditioner with slime coat supplement for stressed fish
• AquaCare Tap Water Conditioner 240ml - budget-friendly option for routine water treatment

Frequently Asked Questions