Keeping your fish tank clean isn’t just about looks—it’s essential for the health and happiness of your aquatic pets. Over time, uneaten food, algae, and waste can build up, making the water unhealthy and the tank unsightly. That’s where a proper deep clean comes in.
While regular maintenance is important, a thorough deep clean every few weeks or months (depending on your tank setup) helps keep everything in balance. Below, we walk you through some essential steps to deep-clean your fish tank the right way, ensuring your fish stay safe and stress-free throughout the process.
Step 1: Prepare Your Tools and Supplies
Before you start, gather all the tools you’ll need to avoid interruptions. Here’s a handy checklist:
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Gravel vacuum or siphon
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Buckets (labelled for aquarium use only)
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Algae scraper or magnetic cleaner
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Aquarium-safe sponge or cloth
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Water conditioner/dechlorinator
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Fish net
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Holding container for fish
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Old towels (for spills!)
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Clean water (pre-treated)
Avoid using soaps or household cleaners, as they can leave behind harmful residues.
Step 2: Unplug and Turn Off All Equipment
For safety reasons, always unplug your tank equipment before cleaning. This includes:
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Heaters
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Filters
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Lights
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Air pumps
Turning off equipment also prevents damage caused by running it dry or while out of water.
Step 3: Remove Decorations and Rinse Separately
Take out any ornaments, rocks, or artificial plants. Rinse them in a separate bucket of old tank water or dechlorinated water. Use a soft brush or sponge to remove algae and debris.
If any decorations are especially grimy, you can soak them in a tank-safe cleaning solution, but never use soap or bleach.
Step 4: Gently Transfer Fish to a Holding Container
Use a fish net to carefully move your fish into a temporary holding container filled with their current tank water. This helps minimise stress and avoids shocking them with sudden changes in temperature or chemistry.
Place the container in a quiet area and cover it loosely to prevent jumping.
Step 5: Siphon Out Water
Using a gravel vacuum or siphon, remove 50–70% of the tank’s water. This allows you to clean thoroughly without disturbing the tank’s beneficial bacteria too much.
Siphon water into a clean bucket and use the opportunity to spot-clean any extra dirty areas.
Step 6: Clean the Glass Inside the Tank
Use an algae scraper or magnetic glass cleaner to remove algae build-up on the tank walls. Be gentle to avoid scratching the glass or acrylic.
If you notice stubborn spots, a clean razor blade (used very carefully) can help—but only on glass tanks.
Step 7: Vacuum the Gravel Thoroughly
The gravel or substrate often holds the most debris. Use your gravel vacuum to gently dig into the substrate, allowing waste and dirt to be siphoned out without sucking up the gravel itself.
Work in small sections to make sure the entire bottom gets attention.
Step 8: Rinse the Filter Media (But Don’t Replace It Yet!)
Remove the filter sponge or bio-media and gently rinse it in old tank water (not tap water). This keeps the beneficial bacteria intact while still removing excess gunk.
Only replace the media when absolutely necessary, and never all at once—this prevents a dangerous ammonia spike.
Step 9: Refill the Tank with Treated Water
Add fresh, dechlorinated water back into the tank slowly to avoid disturbing the substrate or fish once returned. Make sure the new water is close in temperature and pH to the old water.
You can use a thermometer and water conditioner to ensure everything’s safe and consistent.
Step 10: Return Decorations and Fish, Then Restart Equipment
Place decorations and plants back where they belong, then turn your equipment back on—filter, heater, lights, and air pumps.
Allow the filter to run for 10–15 minutes before gently reintroducing your fish to their sparkling-clean home.
Bonus Tips to Keep Your Tank Cleaner for Longer
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Feed fish small portions to avoid leftover waste.
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Add algae-eating fish or snails if suitable for your setup.
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Perform small, regular water changes weekly (10–20%).
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Monitor water parameters with test kits.
A deep clean doesn’t have to be a stressful task—for you or your fish. By following these ten simple steps, you can maintain a healthy, clear, and beautiful aquarium that your aquatic friends will love.
Got a favourite cleaning tip of your own? Share it in the comments below—we’d love to hear how you keep your tank in top shape!