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?

Changing the water in the aquarium is necessary because of the following reasons

  • 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

It is easy to change the water in small aquariums up to 10-gallon capacity.

  • 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 aged 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 kill 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.