An improved disposable filter bag for use with a pool cleaner of the type disclosed, for example, in U.S. Pat. Nos. 5,863,425; 4,558,479; and 3,822,754. The filter bag is formed from a porous filter material having marginal seams formed by direct welding to form a reinforced cuff defining an open bag mouth leading to a hollow bag interior. The cuff is configured for removable mounting on a pool cleaner suction mast, as by removable connection to a mounting collar as disclosed in U.S. Pat. Nos. 5,863,425; D409,341; and D468,067. A divider seam defined by a spaced-apart array of welds subdivides the bag interior into a primary flow chamber for receiving flow of water and water-entrained debris from the pool cleaner, and a secondary collection chamber for trapping and collecting the water-entrained debris.