How to Clean an Old Fish Tank

Emptying the Tank

Take out all the removable items from the tank. Using your hands or a fish net, remove everything from the fish tank that isn’t permanent, including all decorations, plants, rocks, and gravel. This will let you properly clean and sanitize the tank. If you plan to clean and reuse these items, set them aside to be sanitized separately. If the gravel is too difficult to remove by hand or fish net, you may need to use a gravel siphon vacuum to get it all out.

Drain or pour out any old water into a bucket or sink. If the fish tank is relatively small and easy to carry, you can lift the tank and pour any remaining liquid into a bucket or sink. If the tank is too large to lift, place a large bucket on the ground next to the tank and gently tilt the tank so that the water slowly falls into the bucket. Make sure that you use a bucket that is large enough to hold all the old water in your tank. You want to drain it completely. For example, if your fish tank holds 4 gallons of water, you will likely want to use at least a 5-gallon bucket to avoid spillover. If the fish tank is very large, you may need to use a siphon hose to drain the water into a bucket or sink.

Wipe away dirt and residue with warm water and a paper towel. Lightly dampen a paper towel with warm water. Wipe the interior and exterior sides and bottom of the tank with the lightly dampened paper towel to remove dirt and residue. Wiping away the more easily removed dirt and residue will make it easier to sanitize the tank and identify any white residue due to lime or calcium build up, or hard water spots that will need to be scrubbed or scrapped clean.

Sanitizing the Glass

Mix your cleaning solution. It is important that you use a safe cleaning solution so that your old fish tank is properly sanitized. There are several cleaning solutions that you can mix up to effectively and safely clean your old fish tank. Try mixing: Equal parts water and vinegar in a spray bottle. A vinegar and water cleaning solution is excellent for breaking down white residue or hard water stains, neutralizing fishy odors, and safely sanitizing your old fish tank. Add vinegar and water to a clean spray bottle, alternating each to ensure that you have equal parts. Shake vigorously for 10 seconds to combine. 1 part non-detergent bleach to every 9 parts water in a spray bottle. When used in proper concentrations, bleach is perfectly safe to use to clean an old fish tank. For fish safety, it is important that your solution does not exceed 10% bleach. For example, mix 2 ounces (57 g) of bleach with 18 ounces (510 g) of water in a spray bottle. Shake vigorously for 10 seconds to combine.

Spray the cleaning solution over the interior and exterior sides and bottom of the tank. Generously spray to ensure you cover all the surfaces of the tank with the cleaning solution. Make sure to spray inside and around any items that may be attached to the tank. When spraying the outside of the tank, make sure that the tank sits on a bleach-safe or vinegar-safe surface, depending on which solution you choose to use.

Leave the cleaning solution to sanitize for 10 to 15 minutes. If you are using bleach, make sure that you do not leave the cleaning solution on the fish tank for more than 15 minutes. Bleach is a corrosive chemical and can cause permanent damage to your old fish tank if left too long. If you are using a vinegar solution, it is safe to leave the solution on for longer. You can leave a vinegar and water solution on for up to 48 hours without causing harm to your fish tank.

Rinse the fish tank with water and drain with a bucket. Fill the tank with clean water and let it soak for 10 to 15 minutes. After the clean water has soaked, drain by slowly tipping it into a large bucket or sink, or by using a siphon hose.

Let the tank air dry to break down chemicals into harmless by-products. Once the fish tank is drained, let it air dry for 24 hours. This allows any remaining bleach or vinegar to break down, leaving it safe for your fish.

Scrub and scrape any remaining white residue or hard water build up. Using a razor blade or a fish tank safe algae scrubbing pad, scrub and scrape any remaining residue or hard water stains from the walls and bottom of the tank. Once you have scrubbed and scrapped all remaining stains, use warm water and a paper towel to remove any excess debris from the tank. Be sure to use caution when scrapping with a razor blade. Always point the blade away from you with light to medium pressure to avoid scratching the glass. If safety is a concern, you can use an acrylic or plastic razor blade instead of a metal blade. An acrylic or plastic razor blade is less sharp than a metal blade, but should still be effective in removing lime, algae, and calcium build up or hard water stains. If you scrapped a lot of debris into the fish tank, you may need to re-rinse the tank with water to ensure the tank is completely clean for your fish.

Washing the Removable Tank Decorations

Spray the removable tank items with your vinegar or bleach cleaning solution. After you’ve cleaned and sanitized the glass in your tank, you will want to sanitize any tank decorations you plan to reuse. Place all the removable tank items on a vinegar or bleach-safe surface. Spray all the items generously with the cleaning solution and let them soak for 10 to 15 minutes. After the soak, rinse the items under running water to remove all the vinegar or bleach. Let them air dry for 24 hours. You can also mix your vinegar or bleach solution in a large bleach-safe bucket or sink and let the removable tank items soak submerged for 10 to 15 minutes.

Scrub the tank decorations with a fish-safe scrubbing pad or clean toothbrush. Using a fish-safe scrubbing pad, scrub any items that have any remaining build-up, dirt or debris. If the item is small or has hard-to-reach spots, you can use a clean, new toothbrush to help reach into crevices. Rinse the scrubbed items under running water. Pat dry with a clean paper towel or let air dry completely.

Return removable tank items to the fish tank. Once the tank and all the items have been cleaned, you are ready to reassemble your old fish tank and provide a safe and sanitary home for your fish.