But what the person who answered on your last one was right. You don't need a filter if it is a one gallon. I have all of my boys and one of my girls in one gallons to one and half gallons, and I do 100% water changes (remove the fish and dump ALL the water and then rinse out the tank with HOT water then rerinse it with coolish water then refill it and aclimate the fish to the new water and then let it out.) every 3 to 5 days. So at LEAST once a week, usually twice a week.
