The short answer
To get algae off the glass, physically remove it — a magnet cleaner for soft films, a blade scraper for hard green spot — then add grazing snails and fix the light-and-nutrient balance so it stops coming back. Cleaning alone treats the symptom; balance treats the cause.
Cleaning it off
- Magnet cleaner: the easiest routine tool — glide it down the glass weekly to keep soft algae in check without wet hands.
- Blade scraper: for hard, crusty green spot algae that a magnet skips. Hold the blade nearly flat and scrape firmly. See what causes green spot algae.
- Pad by hand: a dedicated algae pad works for soft brown and green films — see brown algae.
Acrylic tanks: use only plastic blades and non-abrasive pads — a metal scraper or grit trapped under the pad will permanently scratch acrylic (and even scratch glass corners). Keep separate pads for the substrate line where grit collects.
Add a cleanup crew
Grazers keep glass and leaves clean between scrapes:
- Nerite snails — the best all-round glass grazers, taking on hard algae most others ignore.
- Otocinclus — gentle catfish that graze soft films on glass and plants.
They won’t fix the root cause, but they dramatically slow regrowth. More on their role in do snails eat plants.
Stop it coming back
If algae returns fast, the tank is out of balance — usually too much light for the available nutrients, or too long a photoperiod. Trim the light hours, match fertilizers to your lighting, and keep up water changes. For the complete strategy across every algae type, read how to get rid of aquarium algae.