Taking care of the fish in your aquarium includes changing the water at required time intervals and doing the deep cleaning by removing all the decorations and other additions. Changing the water is necessary to avoid bad odors and to keep the fish healthy.

Aquariums come in different sizes and according to this the frequency of water changing should be adjusted. Small-sized aquariums need a water change at least once in a week and larger tanks need a water change once in ten days or once in two weeks. Apart from just changing the water, it is necessary to clean the wastes at the substratum at least once a month in the large aquariums.

  1. Why water change is important?
  • When we feed the fish the food particles fall into the substratum and get decomposed slowly this will make the water turn turbid.
  • The food eaten by fish will be released into the water as excreta and this also causes debris deposits in the water.
  • The decomposing particles will release nitrates and phosphates which will cause increased algal growth in the tank and the fish susceptible to diseases.
  • To keep the nitrates and phosphates at the desired level, it is important to change the water.
  • It is necessary to keep the minerals and trace elements at the optimal level for the healthy growth of fish.

Why topping is not enough?

Some people add some extra amount of water to the aquarium without taking out any water from the tank. This is not equivalent to changing water as it will not remove any wastes from the water and the higher level of wastes may eventfully kill the fish.

  1. Changing water in small tanks
  • You will need buckets and mini-gravel vacuum to replace the water.
  • Prepare the water to be added to the fish tank one day in advance.
  • Fill one bucket with water and allow it to stand overnight to remove any chlorine content.
  • If necessary, use de-chlorinator as recommended.
  • Using the gravel vacuum siphon water from the tank to another bucket.
  • Try to vacuum the substrate when siphoning water so that some of the debris builds up will be removed along with water.
  • Remember from a 10-gallon tank; remove only 3 to 4 gallons of water.
  • Add the water slowly through the sides of the aquarium not causing much disturbance to the fish.
  • If you are using electric filters in the fish tank or lights turn off the devices before you attempt water change.
  • After adding clean water plug back the devices.
  1. Changing water in big aquariums

Cleaning and changing water in big aquariums can be really a great task if you do not have the knowledge and the right equipment to do it.  If you are using buckets and siphon to change the water from large tanks, you will get exhausted from carrying buckets of water.

The best and easiest way to change the water in large tanks is to use the water changer. These systems are easy to use. It has a connector for the faucet on one end and a siphon gravel vacuum on the other end.

Step 1: Connect the water changer to the water source following the direction provided by the manufacturer.

Step 2: Flip the lever of the water changer into the draining mode to drain water from the fish tank.

Step 3: Put the other end of the water tube into the aquarium.

Step 3: Take out about 30 percent of water in the fish tank.

Step 4: Use the gravel vacuum function of the water changer to clear some debris at the bottom of the tank.

Step 5: When the water level decreases the tube may pop out from the water so make sure that the tube is always under the water level during the draining process.

Step6: Refill the aquarium by closing the drain lever and opening the faucet.

Step7: Make sure that the tank end of the tube is in a secured position or the water will spill everywhere when you open the faucet.

Step8: If the fresh water added to the tank requires any additives to adjust the pH or de-chlorinator you can add it at this point.

Step 9: Fill water in the aquarium just below the level of filter outlet so that there will not made any strong water currents when the filter is working.


  • Select water changer with appropriate tube length according to the distance from the aquarium to the water source. You can find changers with tube length up to 50 feet.
  • You can drain the water from the tank to your garden or lawn so that you will not be wasting water and the water containing nitrates and phosphates improves the growth of the plants.
  • There is no need to remove or turn off the filter while changing water as you will be taking out only 30% of the water.
  • If you have heaters connected to the tank, make sure the heating element is always below the water level during the draining.
  • Keep a close watch on small fish in your tank as they can get siphoned by the tube.
  • In large tanks, there is no need to match the water temperature as you will be removing and adding only 30 % of water.
  • Make sure that you are not adding ice cold water to the tank. Even a temperature drop of 15 degrees can eliminate some fish.


  • Monthly deep cleaning of the tank is must even if you do water changes weekly. There will be an algal buildup on the sides of the tank and waste deposits on the substrate.
  • The filter systems in the tank also need regular cleaning and maintenance.
  • However, deep cleaning is stressful for the fish as you will be removing the complete set up of their habitat. Weekly water changes can reduce the frequency of deep cleaning needed and will keep your fish healthy and happy.

How often do you change the water in a fish tank?

You should do a 25% water change every two to four weeks. There is no reason to remove the fish during the water change. Make sure you stir the gravel or use a gravel cleaner during the water change.

How do I change the water in my fish tank without killing the fish?

How To Clean Your Tank With Fish In It (Without Killing Them)
  1. Hack #1 — Do Regular Water Changes.
  2. Hack #2 — Vacuum Your Substrate.
  3. Hack #3 — Clean Your Aquarium Filter Media.
  4. Hack #4 — Bleach Your Plants.
  5. Hack #5 — Use Algae Scraper (+Vinegar) on Your Glass.

Do you leave fish in tank when changing water?

Simply topping off the aquarium water as it evaporates puts fish at risk of poor health. When you see the water level has dropped, go ahead and use a gravel vacuum to clean the aquarium gravel and remove more water, then add fresh, dechlorinated water to the aquarium to bring it back to the proper level.

Can I add water conditioner while the fish are in the tank?

You can put a water conditioner while the fish are in the tank since water conditioners are generally safe to use. However, it would be best to remove the fish in small and overcrowded tanks for at least 15 minutes. That will allow the conditioner to diffuse equally across the entire aquarium.

Can I change my fish tank water everyday?

If you dechlorinate properly and always bring water to the same temperature, there is actually no limit on how often you can change the water. Professional fish breeders may change water daily in order to remove excess food and encourage maximum growth.

Do fish like water changes?

The answer is that regular water changes are important for the long-term health of your fish. The dissolved wastes in the water, which are not apparent to the naked eye, won’t eliminate the fish outright, but the stress reduces their immunity to disease.

How do I make my aquarium water crystal clear?

  1. Filtration. Filtration is the most fundamental way that we keep aquarium water clear.
  2. Chemical filtration. Chemical filtration works by absorbing or adsorbing things from the water.
  3. Bacteria. Some strains of bacteria can also be added to aquarium water to help to clear it.
  4. Fish.
  5. Food.
  6. Water changes.
  7. Flocculants.
  8. Light.

Do fish recognize their owner?

Of course, different species of fish will have different abilities, as well as different levels of vision. In most cases though, yes, fish are able to recognize their owners and in some cases form an attachment. The fish will come over to their recognized owner who often offers a food treat or reward.

Do fish get bored living in a tank?

We know that the nature of a fish’s tank will have an influence on its brain and behaviour. This could be the aquatic equivalent of the pacing of a captive tiger that’s bored from a lack of stimulation. But the fish could also be stressed from an overcrowded or unfamiliar tank.

How do fish show affection?

Researchers have found that fish recognize each other and gather information by eavesdropping. They’re capable of remembering past social interactions that they’ve had with other fish, and they show affection by rubbing against each other.

Do fish get sad when other fish die?

No, fish do not getsad” if another fish dies. Fish do have a brain that is capable of some type of “emotion” but not to the extent that humans feel. They don’t feel anything like sadness, but may feel something to a smaller extent. Scientists have been able to train fish.

Do fish like being stroked?

Yes, some fish like being petted.

So, of course, not all fish (like sharks) like to be touched and caressed. Some fish, like groupers, really enjoy being petted. Fish like to be caressed gently. They can even get used to it and can come up to be petted.

Do fish know their name?

Unlike a dog, fish probably won’t respond to their names. They can also be a wordplay on the appearance of the fish, their colors, patterns, eyes, tail, and more. You can also search the scientific name for your fish and use that to inspire you in choosing its name.

Can fish hear you?

But can your fish hear you? The answer is… Yes, fish can hear your voice and will often associate it with a particular action. If you talk to them just before you feed them, for example, they’ll often swim to the top of the tank as soon as they see you or hear you speak.

How do fish see humans?

How do fish see us? Science tells us that fish have eyes similar to humans, but they also have protective film over their eyes so that they can see more clearly underwater. Their eyes have rod and cone cells on their retinas, so we know that they can see color as well as in shades of grey, light and dark.

Do fish remember being caught?

We’ve found through our studies that fish do have a memory. “It’s the same way for the fish’s buddies that observed that fish being caught, too. When they see the lure come past, they are going to remember and they are going to avoid it.” The same holds true for lakes that are exposed to heavy fishing pressure.