12' pool w/ 2' of water => 1,700 gallons of water.

1. Read the Super Simple Recipe => http://pool9.net/ssr/
2. Get some new cartridges, preferably Unicels (see SSR, above)
3. Drain the pool COMPLETELY, and restart using the SSR

The small soft-side pools are extremely difficult to clear: their filter systems are barely large enough for ideal conditions, and simply take forever to clear the water once something goes wrong. With the very small pools like yours, it's easier and cheaper to start over than to try to clean things up. And it's MUCH faster.