Sequestrants 'work', though some work rather poorly, and I suspect none 'work' the way you mean. All they do is keep iron (or other metals) dissolved; they don't get rid of them

The ONLY way to get rid of the metals, is to get them out of the pool,
  • by causing them to settle to the bottom of the pool, and then vacuuming them out, OR
  • by filtering them out, OR
  • by using the CuLator* units to capture them, while they are still soluble.
So, having a cartridge filter "get dirty quick" is EXACTLY what you want, because when you wash that dirt off, you have removed that much of the metals. The small filters that come with Intex pools make it harder to remove them, either because they fail to capture the metals, OR because they stop up so quickly.

Getting a LARGER Intex filter will make it easier, as will replacing they Intex cartridges with higher grade US-made cartridges that will last all season, if properly cleaned each time. This is pretty easy to do IF you have a least a pair of cartridges, and preferably, with metals, three cartridges.

* We think, but are not completely sure yet, that these work more or less as claimed.