How to Clean Aquarium Glass Inside and Out — Toronto Home Guide

Aquarium glass develops two distinct types of build-up: algae growth on the interior surfaces (green, brown, or black) and mineral deposits (white calcium carbonate haze) on the exterior and along the waterline. These are cleaned differently and require care to avoid harming the tank's inhabitants.

Interior Glass (Algae Removal)

1. Use an aquarium-specific algae scraper or magnetic glass cleaner — a razor blade scraper for glass tanks or a plastic scraper for acrylic tanks (metal scratches acrylic)
2. Work the scraper in long, overlapping strokes from top to bottom to dislodge algae
3. For stubborn green spot algae: a new single-edge razor blade held at a low angle removes it effectively from glass (not acrylic)
4. The dislodged algae will float in the water — a water change after cleaning removes most of it; the filter handles the rest
5. Never use household glass cleaner, soap, or any chemical inside the tank — even trace amounts are lethal to fish

Mineral Deposits on the Waterline (Exterior)

1. Wet a cloth with undiluted white vinegar and press it against the mineral deposit for 5–10 minutes
2. Scrub with a non-scratch pad — the deposit should dissolve and wipe off
3. Rinse the exterior glass with clean water to remove vinegar residue before it can evaporate and create a smell near the tank
4. Dry with a clean cloth

Exterior Glass

• Use a damp microfibre cloth for the exterior — no glass cleaner; ammonia-based cleaners near an open tank can affect water chemistry
• For a streak-free finish: a solution of equal parts water and white vinegar applied with a microfibre cloth works safely near an aquarium

Preventing Algae Build-Up

• Limit light exposure: algae grows from light and nutrients; keeping lights on for 8–10 hours maximum per day and not placing the tank in direct sunlight reduces growth significantly
• Live plants compete with algae for nutrients and CO2 — they are one of the most effective long-term algae control methods
• Algae-eating species (otocinclus catfish, nerite snails, bristlenose plecos) control glass algae effectively in freshwater tanks