In the literature one finds different times to establish a tank fauna - although a couple of weeks full of water and a few snails, maybe some plants and the tank is ready for fish and water changes. Cycling through the different chemical forms of nitrogen compounds is complex and seldom really happens completely in a tank as small as 10 gallons unless there are only 3 to 5 small fishes present. In your case an UGF can be a lot of help. They get dirty and develop that tank fauna which helps in the cycling process. There are still problems though- and the only way is to flush the toilet once in a while.

The small fish tank is truly a septic tank. Septic systems depend on bacteria, plants and surface area to break down the waste - but even the best septic tank gets fresh water almost continually - each time the toilets are flushed and dishes are washed, etc. into the overflow  - - "The Grass is Always Greener over the Septic tank". partly because of the Nitrogen fertilizer and partly because of the overflow and the area is almost always wet.

Beginner or experienced keeper, one knows the water the wild fish live in is continuously changed and renewed. The water is always new but the surroundings are almost never completely changed. All the plants and animals live there with 100% water changes moment by moment. And I still argue that tank water should be changed as often as time permits - or take time to do it. Still the tank has to have that "cycle" to get established.

You will grow larger, more healthy fish in smaller quarters with more frequent and more complete water changes.

Should one change all the water in a fish tank regularly? - only after the tank is established. How often should one clean a tank? When something devastating happens. Most people don't have the resources to replace tank water in very large amounts due to the chlorination of the public water supplies. Fresh tank water must be chlorine free and should be both the same temperature of the outgoing water and have the same O2 and salt level concentrations. That part is hard with out a reservoir of some size. (I use a 55 gallon plastic drum, w/ air and water pump for circulation but that changes only a third of my tanks so it has to be refilled at least twice before I am done)

Aside note: Most everybody has established "Their way" of doing things and have achieved various levels of success. 'Moderation in all things' is what my parents taught me and it seems to ring through everything I have been successful in to include the fish hobby. We all develop our own ways after a few accidents and over reactions - but don't expect to make all the mistakes - learn from us who have made some of those mistakes so you won't have to repeat them.

and . . . change as much water as often as you can . . .