To understand this better you need to realize that your aquarium is a little ecosystem on its own and if you clean it to much there is not enough good bacteria to keep your fish healthy. On the other hand it is a closed system that has to be maintained by you, so not cleaning your aquarium often enough will leave your aquarium dirty with unhappy fish.
So how much cleaning and how often will be ideal? This all depends on how big your aquarium is, how many fish of what size do you keep and what kind of filtration do you have. Here is an example which you can follow and adapt to your own circumstances for good aquarium maintenance.
In a 15gallon or 60litre fish tank with one corner filter(with filter wool and activated charcoal) and a fish population consisting out of the following:
- 1xCommom Pleco
- 2xPeppered Corydoras
- 2xBleeding Hart Tetra
- 2xBlack Skirt Tetra
- 4xRummy Nose Tetra
- 7xBlue Neon Tetra
- 4xHarlequin Rasbora
- 4xZebra Danio
- 2xMarble Hatchet Fish
and three live plants.
In a tank like this you can clean the aquarium gravel twice a month and replace the filter wool and charcoal once a month. Alternate the cleaning of the filter and the gravel to maintain a sufficient level of good bacteria.
The gravel and filter are both places where good bacteria is found. Since you have to clean them both it is a good idea to alternate the cleaning of these two in order to maintain sufficient levels of bacteria.
With no intentional breeding taking place in this tank, your fish will be healthy and happy and you will not spend hours each week cleaning the tank.