This is an article I published for Helium last year on aquarium maintenance.
Having an aquarium in your house can be so fun for every member. We have kept tropical fish for years and love the hobby. Keeping fish as pets means making sure they are happy (as you would do for any pet), by doing partial 20% water changes, checking the heater and water temperature, and checking and changing the water filter.
Partial water changes can and should be done on a weekly basis unless you have cloudy water, the water changes would be daily 20% changes in that case. If your water looks green, like my tank in the past had been, the sun from a nearby window is too strong. An easy fix is blocking some light from the window and also covering up the back and sides of the tank if needed with construction paper or a poster.
The heater and filter should be checked daily to make sure that they are running properly and those can be checked along with the actual fish while you are feeding them. Filters should be changed every two to four weeks. I find the rule of thumb with filter changes is changing small tanks, two to ten gallon tanks every two weeks, and larger tanks, 20 and above, every four as long as you don't over- love your fish by over feeding them.
Following these simple steps to ensure happy fish will give your fish a happy place to live. I also find that keeping fish gives me a way to relieve stress, because when I keep the fish happy, I'm keeping myself happy as well.