If there is one golden rule about cleaning aquariums it is to NEVER use common cleaning supplies like dish soap, chemical wipes, or sponges. The chemicals found in these common cleaning supplies will harm your fish and damage your carefully balanced ecosystem. Best practice for cleaning aquarium equipment is to use good old fashioned elbow grease.
Aquarium supply companies will sell aquarium safe sponges that are specially designed to be safe for use in the aquarium. Avoid common household sponges; these are likely to contain trace amounts of chemicals that add to its sanitary qualities. Many companies explicitly label their products as “Not for Aquarium Use”.
When you pick out your aquarium-only sponge, be sure to think about what surface you are using it on. Acrylic tanks are easily scratched by rough sponges or straight edge scrapers. Acrylic aquariums have special cleaning equipment that is designed to be gentle on these soft surfaces. Glass tanks are generally harder and you can use more abrasive sponges and even straight edge metal razors. Be warned, it is still possible to scratch a glass aquarium if you are not careful.
Your aquarium is like a studio apartment with no doors or windows. When things start to get stinky, there is no option to open a window and let in some fresh air. The only way freshen things up in your aquarium is to perform a water change. By removing old aquarium water and replacing it with clean water, you are doing your fish a great service by removing traces of nitrogenous waste. Depending on the size of your tank and the number of inhabitants, you should perform 10-25% water changes every other week.
Fish waste and uneaten food might not always make it to your filter and will settle between the cracks in your gravel on the bottom of your tank. Much like vacuuming a rug, there are aquarium-made Gravel Vacuums that help suction out the detritus. This is a great way to make sure you are keeping your water clean and should be a regular routine that coincides with water changes.
Depending on your filtration, your filter media will need to be replaced or cleaned. There are a variety of different filter types, but most include straining dirty water through a sponge-like filter. These filters should be regularly removed and rinsed with fresh water to remove large pieces of detritus and improve their efficiency.