How to Clean Aquarium Glass Inside and Out Without Scratches

Unplug before your hands go in

Fluval’s AquaClear filter manual: “Always unplug or disconnect all appliances in the aquarium from electricity supply before placing hands in water, before putting on or taking off parts and while the equipment is being installed, maintained or handled.” Stay unplugged until step 9, then plug every appliance you unplugged back in.

Clear grit off the tool and the glass

Tunze, on its Care Magnet, says “scratches can occur due to adhering particles such as sand or dust” and: “Please ensure before each use that both the contact surfaces of the cleaner and the glass are completely free of contaminant objects.” Stay unplugged until step 9.

Clean the glass, keeping a sharp blade out of the corners

Stay unplugged until step 9. Green Aqua, an aquascaping retailer, writes of an algae scraper with a “sharp stainless-steel blade”: “The algae scraper should not be used in the aquarium corners, as the silicone bonding could be damaged. Therefore, the best practice is to keep a small safety distance of about 0.5cm from the corners.” (About 0.2 inch; our conversion.) And: “When handling the algae Scraper, be careful not to get into contact with the sharp blade. Therefore, it is also highly advisable to keep the algae scraper out of the reach of children.”

Magnet: match it to the glass

Aqueon rates its Small magnet for “glass or acrylic aquariums up to 20 gallons or 1/4″ thickness”; its “bowed bottom design allows the scrub pad to rest above the gravel for easy retrieval while reducing the risk of scratching the aquarium walls.” Its scrubber “will fall straight down if separated”. Titan Aquatic Exhibits, an acrylic aquarium builder: “It’s important to use a magnetic algae scraper appropriate for the thickness of the glass of your aquarium. Using a magnet that may be too strong could damage the acrylic surface.” Tunze, on its Care Magnet strong: “We expressly do NOT recommend using the Care Magnet on ACRYLIC!” Our glass cleaner roundup quotes two magnet makers’ manuals (linked in Sources). AQQA, an equipment brand, opens its AQ208 manual with “WARNING: Do not use stainless steel blades in acrylic aquariums.” and adds: “Please use caution when using this powerful magnetic cleaner, and do not pinch your fingers between the two parts.” “Please keep the magnetic cleaner away from children.” “The magnetic cleaner is unsuitable if you wear a pacemaker or have a defibrillator implanted.” hygger’s 953 manual warns: “Do not use stainless steel blade for acrylic aquarium. Do not put your fingers between the grip and the black scrubber pad, be careful of your fingers being pinched by the cleaner” and: “Please keep the magnet cleaner away from children, due to strong magnetism.” “Please don’t wear pacemakers and implanted heart defibrillators devices when you use the magnet cleaner.” “Please more caution with this very strong magnet, do not put your fingers between the two pads, simply rotate 1/4 turn to separate cleaner.” Reach in for a dropped scrubber only while everything is unplugged. Stay unplugged until step 9.

Pad on a handle: glass only

API: “For glass aquariums only. Do not use on acrylic, Plexiglas, or any surface other than glass. Do not use on dry surfaces. Rinse pad with tap water before and after each use. Caution: If aquarium gravel is picked up on pad, wash off before using since gravel will scratch glass surfaces. Do not use pressure so extreme that scratching or breaking of aquarium glass occurs.” Stay unplugged until step 9.

Acrylic: test the tool first

API, for its acrylic scraper, repeats the dry-surface and rinse lines, then: “Caution: if aquarium gravel is picked up on pad, wash off before using since gravel will scratch acrylic surfaces. Do not use pressure so extreme that acrylic scratches or breaks.” Continuum: “Acrylic safe blade is necessarily soft and can therefore pick up sand or small bits of gravel if shoved too hard down into the substrate.” It says to check the plastic blade “periodically by running a finger or thumbnail across the surface”, and: “Some aquariums are made from low grade imported acrylic that is extremely soft and of very poor quality that can be easily scratched. User must exercise proper judgement in use and should test blade in an inconspicuous area prior to use to insure compatibility.” Stay unplugged until step 9.

Let the algae settle, then siphon it out

Aqueon follows the glass with a gravel-vacuum water change (our water change guide covers it): “The siphon will now be able to suck up the loose algae that has settled to the bottom.” Give the heater its maker’s wait, counted from when you unplugged it, before you drain. Hydor’s support page: “When undertaking water changes Hydor recommend that the heater is turned off and unplugged from the power socket at least 30 minutes before any waterchange.” Its Theo manual: “To avoid possible breakages due to thermal shock, the heater should be disconnected from the power supply at least 5 minutes before taking it out of the water or before adding or changing the water.” Where a maker’s pages differ, as Hydor’s do, or you have no manual, our reading is the longer wait: 30 minutes, Hydor’s longer figure. Stay unplugged until step 9.

Refill with treated water

Aqueon: “add water conditioner to new water and then refill the aquarium. Be sure to match temperatures of the new water with the aquarium.” Stay unplugged until step 9.

Plug every appliance you unplugged back in, once the tank is full and your hands are out

Aqueon: “Plug the filter and heater back in.” Fluval’s AquaClear manual, for its own filters: “Do not allow filter pump to run dry.” After you clean an AquaClear, it adds: “Follow operating instructions to restart and prime power filter.” Hydor: “The Heater can ONLY then be turned back on when the Aquarium is full and the heater is completely submerged.”