Depending on which types of fish, age of water and also the type of aquarium supplies that you have, generally a good rule of thumb is to carry out aquarium cleaning by performing partial water change (at least one-third of the water) every once a week. Certain fish such as discus will require more attention while other fish such as guppies will require less frequency of water change since they can tolerate wider range of water parameters. Age of aquarium is also another determining factor as older and more established aquarium will have a constant population of beneficial bacteria that naturally breaks down harmful chemical like ammonia and nitrite and thus it is less imperative to change the water that often. If you have high capacity aquarium filter which can take in higher volume of water then the frequency on aquarium cleaning can also be reduced because the filter media will take longer time to choke up and become concentrated.
During aquarium cleaning, it is not necessary to always remove the fish from the aquarium. This is important to reduce stress and to avoid subjecting the fish to injury during movement from one place to another. While performing your water change, make sure that the water is first siphoned out up to the desired level, then slowly remove some of the decorative items to take out and wash. If your aquarium is covered with gravel bed, then I would suggest getting an aquarium gravel cleaner (see attached pic) to simply the task. Don’t worry about the fish rushing around and finding a place to hide because once they become adjusted to the routine, it will become less stressful to them. Also make sure that each time you perform the cleaning, cycle time needed to complete the task should somehow be reduced as you become more well-versed with it.
Next, you should also take out the filter media and rinse it properly in a bucket of clean water. Do not add in any chemicals for the washing because there might be risk of the chemical carry over in case you do not rinse it properly and thus ended up poisoning your fish tank instead. Chemicals will also kill beneficial bacteria and therefore, it is not a good idea to use this at all. Once you have put back in every accessories that you have taken out, it’s time to fill the aquarium back to its original water level. After you have done with the aquarium cleaning, don’t forget to check the water quality especially on pH checking using water test kits.