How often to do water change/clean a 3gallon tank

[MommaOkie]

Ok finally upgraded Ripley to a 3 gallon tank. It has an undergravel filter (I hate those but it was the only option in the size I needed) and has an air pump (stone type). The temp is kept at 78 and he is the only thing in the tank. I also recently switched from pellet food to flakes if that makes a difference. My question is how often do I need to clean the tank or do water changes? I tested before I added him to the tank this morning and everything was right in check, will test the water after he's been in a day or so too. I should also add it is an uncycled tank (I know its better to cycle but tell that to a 10 year old screaming he wants a new tank LOL!) I did run it for about a week before we added him.

[Oldfishlady]

You can safely establish the nitrogen cycle with the fish provided that you make the needed water changes, however, often with the smaller tanks due to limited surface area for the bacteria to colonize the cycle isn't always stable.....

Regardless of cycling stage on a 3gal with an UGF-you will need to make at least twice weekly water changes....1-50% water only and 1-50% with deep vacuum of the substrate-it is important with UGF that you keep the plates clean so that they will function properly.....

Love to see some pics.....