Why glass gets dirty
A thin film of algae on the viewing panes is completely normal — it is simply algae growing on a well-lit surface, and every healthy tank gets some. Your job is to keep it in check on the front and side panes so you can see in clearly. If it returns very quickly, that is a clue about the tank rather than the cleaning: usually too much light or too many nutrients, which our algae guide covers. For a quick answer on the glass specifically, see getting algae off the glass.
Cleaning the inside glass
The inside panes are where visible algae builds up, and there are two main tools for the job.
- Magnet cleaner: two magnets sandwich the glass — you move the outer one and the inner pad wipes the algae off, no wet sleeves required. Ideal for routine weekly cleaning. See our best magnet cleaner pick and the comparison in Mag-Float vs Flipper.
- Scraper or blade: a dedicated aquarium glass scraper handles hard, crusty green spot algae the magnet skips over.
Work top to bottom so loosened algae falls toward the substrate where you can remove it, and keep the magnet or blade off the substrate line to avoid trapping grit that could scratch the glass.
The golden rule: no soap, ever
This is the one thing you must never get wrong. Household glass cleaners, soaps and detergents leave residues that are toxic to fish and invertebrates, and even a trace can cause harm. Nothing chemical belongs in or near the water.
Cleaning the outside glass and hard water marks
The outside panes pick up dust, fingerprints and, over time, chalky white water spots where splashes have dried and left mineral deposits. For everyday smears, a clean cloth dampened with plain water is enough. For stubborn hard-water marks, a cloth lightly dampened with diluted white vinegar works well — but spray it onto the cloth, not the tank, and keep it well away from the water surface, then wipe over with plain water afterwards.
- Use a lint-free cloth for a streak-free finish.
- Dampen the cloth, never spray directly above an open tank.
- Wipe the rim and lid too, where evaporation leaves the worst mineral crust.
Keeping glass clean for longer
The less algae grows, the less you clean. If the glass clouds over within days, treat the cause rather than just the symptom: shorten the lighting period, feed a little less, and keep up regular water changes. A small clean-up crew such as Otocinclus or nerite snails will graze the panes for you between cleans. Slow the algae at its source and the weekly wipe becomes a quick, satisfying finishing touch — see the maintenance hub for the full routine.