How to Change Fish Tank Water

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This article was co-written by Craig Morton. Craig Morton is the CEO of Aquarium Doctor Inc. is headquartered in Huntington Beach California and provides services in Orange County, Los Angeles County and the Inland Empire. With over 30 years of aquarium experience, Craig specializes in creating custom aquarium designs, along with aquarium maintenance and installation. Aquarium Doctor works with manufacturers and products such as Clear for Life, Sea Clear, Bubble Magus, Tropic Marine Centre, Salifert, ReeFlo, Little Giant, Coralife and Kent Marine.

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You should change the aquarium water at least once a week if it is not possible to change regularly. Regular aquarium cleaning has two purposes. Firstly, it will wash away the bad smell from the aquarium. Second, it will keep your fish healthy. If you notice that the glass in your aquarium is starting to fog up, it’s time to replace the dirty water with clean water.

Table of Contents

Transfer fish

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Find a storage tank. The fish will need to be placed in a temporary tank while you wash and refill their current tank with fresh water. So look for a properly sized fish tank, bucket or pot that will serve as a temporary fish tank. ^{[1] X Research Source}

Use a tank or basin that has not been washed with soap, as leftover soap can be harmful to the fish. ^{[2] X Research Source}

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“Water treatment. You will need to treat the water that will be used in the tank temporarily to balance the temperature and pH. Leave overnight after filling the temporary tank and wait for the chlorine concentration in the water to neutralize. ^{[3] X Research Sources}

If you’re not going to wait for the water to treat overnight, be smart about treating it with a dechlorinator. These products neutralize the chlorine concentration found in most municipal and municipal water supplies. ^{[4] X Research Sources}
Make sure the water in the temporary tank is the same temperature as the water in the current tank. You may want to put a lid on top of the tank to prevent the fish from jumping out.

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Avoid direct light. The temporary tank should not be placed at a window or under strong light, as the heat from these places can raise the water temperature, silently harming the fish. Also, make sure to place the temporary tank in a place where children and pets can’t disturb the fish. ^{[5] X Research Sources}

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Transfer fish. Use a racket to remove the fish from the tank and place them in a temporary tank filled with clean water. Use a large bowl as a temporary tank to give the fish enough space to swim. ^{[6] X Research Sources}

When using a racket to transfer fish from one tank to another, make sure the two tanks are close together. This will limit the amount of time the fish is out of the water, thereby reducing stress levels in the fish. ^{[7] X Research Sources}
Alternatively, you can use a small clean tank to transfer fish. Make sure the tank doesn’t stick or soapy residue and choose a round tank with smooth edges. When applying this method, you just need to dip the small tank into the large tank and wait for the fish to swim in. Be patient and don’t chase the fish around its tank. This can be stressful for the fish. ^{[8] X Research Sources}

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Fish tracking. While cleaning the aquarium, make sure you keep an eye on the fish in the temporary tank. Look for changes in their behavior, color, and activity level. The following signs will indicate that the water in the tank is temporarily too warm. ^{[9] X Research Source}

Hyperactivity.
Color change in fish
“Swallow” to the surface (although some fish, like the labyrinth, breathe this way)
If the water is too cold, your fish will show the following signs: ^{[10] X Research Source}
Inactive
Lying on the bottom of the tank
Discoloration

Clean the existing aquarium

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Discard dirty water. Pour the old water out of the current tank. Use a racket, sieve or filter to keep solids from falling out of the tank and into the drain. You can also pour dirty water into the garden or potted plants. ^{[11] X Research Source}

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Wash the ornament. Scrub off the gravel and decorations in the aquarium with warm water with a little salt. For best results, place gravel and decorations in a sieve and scrub with hot water in the tub. Once that’s done, set them aside and let dry. ^{[12] X Research Source}

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Fish tank cleaning. Scrub the aquarium with warm water and a little salt. Avoid using soap and water cleaners as they can leave chemical residue inside the tank. Then rinse the tank with warm water. ^{[13] X Research Source}

If you see a significant build-up of limescale in your aquarium, scrub it off with vinegar, then rinse off the vinegar with warm water. ^{[14] X Research Source}

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Let the tank dry. After rinsing and rinsing the aquarium, let it dry for about 20 to 30 minutes. This will allow the glass surface in the tank to dry after being exposed to warm water used for cleaning. Waiting a while for the tank to return to room temperature will help ensure that the tank is at an ideal temperature when the fish return. ^{[15] X Research Source}

Fill the fish tank

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Return hard objects to the tank. Add gravel and decorations to the cleaned aquarium before adding fresh water to the tank. Make sure everything is in the same arrangement as the original so as not to upset the fish by changing their environment. ^{[16] X Research Source}

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Pour clean, treated water into the tank. Pour into a bath of treated room temperature water or leave overnight to get room temperature. If you use a dechlorinator, be careful not to spill it, as it can leave a chemical smell on the carpet or furniture. ^{[17] X Research Source}

Again, you may want to use a dechlorinator instead of waiting overnight for the chlorine concentration to neutralize. If so, make sure the water temperature is the same before returning the fish to the tank. ^{[18] X Research Sources}
Make sure you cover the water tank or keep it out of reach of pets or children. This will keep the water from getting dirty while it’s being treated.

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Move fish. Scoop the fish out of the temporary tank with a racket or small bowl. Try to move the fish as quickly as possible to avoid stressing the fish. Also, be careful not to drop the fish or let them jump, as they can be seriously injured if this happens. ^{[19] X Research Source}

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Return the fish to the original tank. Return the fish to a tank filled with fresh water. Gently lower the fish into the water with a racket or bowl. Do not drop fish directly into the tank. ^{[20] X Research Source}

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Fish tracking. Fish are most likely to experience stress and environmental and temperature related illnesses during and immediately after washing their tanks. Therefore, always keep an eye on the fish after re-entering the tank to ensure they are well adapted to the clean environment. ^{[21] X Research Source}

Advice

Treating the water in the aquarium will help keep the fish’s habitat cleaner and you’ll have to change the water less often. Discuss water treatment with a professional or someone who works at your local pet store.
Make sure you don’t buy too many fish or choose fish that are too big for the tank.
If you don’t like water treatment, use bottled spring water instead of dirty water.
Never do a 100% water change. It will take away beneficial bacteria and can shock the fish when released into the tank. Your fish may also be shocked by the change in water temperature.
It is better not to keep fish in small tanks. They are too small and cannot fit the purifier and heater. Siamese and goldfish both require large tanks and filters, especially with goldfish. Goldfish grow very fast!

Warning

Make sure the water in the temporary and existing tanks is dechlorinated and at room temperature before transferring the fish to either tank.
If you are using a dechlorinator, follow the manufacturer’s instructions carefully to protect the fish.

Things You Need

Aquarium
Pebbles
Temporary tank for fish while you change the water
Small eye sieve (optional)
Dechlorinator (optional)

Steps