How often should I clean my betta tank?

I have a betta in a 1 gallon mini-bow with undergravel filter.how often should I change water in the tank? im going on holiday soon and need to know when to change water so its ready to him.also, the air pump is really annoying because all bubbles in the tip of the tank.how I can avoid so many bubbles out? thank you very much! http://www.petco.com/product/15340/All-Glass-Mini-Bow-1-Junior-Aquarium-Kit.aspx

undergravel filters are good but not as good as bedside or power filter. this is due to waste and the food is still in the water just under a fence. so if you allow sufficient time still poison the tank. to do complete water changes every 10 days. As for the bubbles, mine reached near the water surface, so I have to cut out the bubble tube.

Aquarium Air Pump