This is my 10 gallon nano. Soft corals only, cheapo led light. One powerhead, one heater (both covered by that pile of macro algae) and that's it. I occasionally run that power filter on the left but it's typically off. I have 2 small clowns as well as 3 or 4 sexy shrimp.
This is my easiest tank but I make it easy. Whenever I feel like it I change anywhere from 10-75% of the water. I say this because once a week I am doing water changes on other tanks so I simply recycle some water from another tank and it ends up in here. If the 10 gallon is your only tank then I would recommend at least some basic testing, but this size tank makes it real easy to just do a weekly water change to replace trace elements.