Aquarium algae scrapers: how to clean the glass without scratching

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Stock checked on October 7, 2026

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Aqueon Aquarium Algae Scraper, Fish Tank Magnetic Glass Cleaner… 9.0 ★★★★★ AcuarioSano rating: 9.0 out of 10 See price

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Aqueon Aquarium Algae Scraper, Fish Tank Magnetic Glass Cleaner… 9.0 ★★★★★ AcuarioSano rating: 9.0 out of 10 See price

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HOTOOLME Aquarium Scraper, 25.6" Stainless Steel Scraper… 8.4 ★★★★★ AcuarioSano rating: 8.4 out of 10 See price

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Why algae grows on the glass

Even in a well-balanced tank, the glass slowly picks up a thin film of green algae or hard green spot algae. That's normal: there's light, nutrients and a smooth surface. If the film comes back within two or three days or gets thick, the real problem is too much light or too many nutrients, so read our guide to aquarium algae before buying more tools.

Most people scrape the glass once a week, right before the water change. That way the loosened gunk ends up in the bucket instead of the filter.

Types of algae cleaners compared

Type	How it works	Pros	Cons	Best for
Magnetic glass cleaner	one half inside, one outside, held by a magnet	dry hands, quick daily use	can trap sand grains and scratch	weekly cleaning of light film
Floating magnet	the inner half floats if it detaches	no fishing around at the bottom	slightly less grip on thick glass	tall and deep tanks
Metal-blade scraper	steel or razor-style blade on a handle	removes hard algae and green spot	scratches acrylic and silicone	glass tanks only, stubborn algae
Plastic-blade scraper	rigid plastic or ABS blade	acrylic-safe	less effective on hard algae	acrylic tanks and nanos
Pad or sponge on a handle	mildly abrasive pad	cheap, reaches corners	wears out, some pads are too abrasive	nano tanks and touch-ups

Brands like Flipper, Mag-Float, Fluval, Tetra, JBL, Eheim and Hygger sell magnets in several sizes and long-handled scrapers. In practice, many hobbyists pair a magnet for routine cleaning with a blade scraper for the algae that won't budge.

Glass thickness and tank material

• Thickness: every magnet lists the maximum glass thickness it handles. Nano tanks with 3/16 in (4-5 mm) glass need a small size; 30-55 gallon tanks (100-200 liters) with 1/4-3/8 in (6-10 mm) glass need a medium or large one. A magnet that's too strong for thin glass snaps together and can pinch fingers or crack the glass.
• Glass: fine with metal blades, as long as you stay off the silicone seams.
• Acrylic: scratches very easily. Use only acrylic-rated magnets and scrapers with soft felt and plastic blades.
• Curved glass or corners: flat magnets don't sit well; a sponge on a handle works better.

How to use it without scratching

1. Start at the top and work down, leaving about an inch (2-3 cm) above the substrate.
2. Clean the bottom strip with a handled scraper, not the magnet.
3. With a metal blade, keep a low angle and stay at least half an inch (1 cm) away from the silicone.
4. Rinse the magnet pad now and then to remove particles.
5. Clean before the water change, with the filter running.

Common glass-cleaning mistakes

• Dragging the magnet across the bottom and getting sand under the pad.
• Using kitchen scrubbers or sponges with soap or detergent residue.
• Running a metal blade over an acrylic tank or along silicone seams.
• Buying a magnet too small for the glass thickness: it slips and doesn't clean.
• Cleaning more and more often instead of fixing too much light or food.
• Forgetting the outside: hard-water spots and dust on the outer glass block light too.

For this comparison we review spec sheets, verified reviews and real-world use criteria, but we don't physically test the products.