The short answer
You never remove the fish (or all the water) to clean a tank — that’s an old habit that does far more harm than good. Instead, do a partial water change with the fish in place: siphon out 25–30% of the water while vacuuming the gravel, wipe the glass, and refill with dechlorinated, temperature-matched water. The fish stay calm and your beneficial bacteria stay alive.
Why not empty the tank
Netting fish out, tipping the water away and scrubbing everything “clean” is one of the most damaging things you can do. Most of the tank’s beneficial bacteria live in the water, gravel and filter — strip them out and you destroy the biological filter, which causes a dangerous ammonia spike when the fish go back into fresh water. It’s stressful for the fish and often fatal. A partial change keeps the ecosystem intact, so the tank stays stable. See what causes an ammonia spike.
The safe cleaning routine
With the fish still swimming, work through this each week or two:
- Vacuum the gravel with a siphon-fed gravel cleaner, drawing out 25–30% of the water as you go. This lifts waste from the substrate and does the water change in one step.
- Wipe the glass with an algae pad or magnet cleaner before you refill.
- Trim plants and remove any dead leaves or leftover food.
- Refill with dechlorinated, temperature-matched water, poured gently so you don’t stress the fish.
Our step-by-step water change guide covers the method, and you’ll find tools in the maintenance hub.
Keep it regular, keep it gentle
The secret to an easy-to-clean tank is consistency — small, regular partial changes keep it clear far better than occasional deep cleans. Clean the filter separately, rinsing the media in old tank water (never under the tap) on a different day so you don’t disturb the bacteria in tank and filter at once. Follow a simple maintenance schedule and the tank rarely needs more than this light, fish-safe upkeep.