I am having a tough season with evaporation and/or pool water loss so I need to keep filling pool. There a lot metals in long island water so my water is not as crystal as I like (and a few minor stains). Does anyone recommend Jacks Purple or something cheaper???
...I have a SWG.

The ascorbic acid treatment is typically used to remove stains:
ascorbic-treatment-to-rid-pool-of-metal-stains-t2298.html

After they're gone, a sequesterant like Jack's will keep them from depositing again. Phosphonic acid derivatives (like HEDP) are the best sequesterants, but I don't know what the cheapest one is. Metal Free is not the same kind.

Our fill water from a well has trace amounts of Iron and over time it causes stains.
I used Jack's Magic Purple Stuff for 2 seasons in our saline pool and it worked well.

I am currently testing the Blue Wave brand of Super Rust & Scale Remover.
It is an HEDP based sequestering agent at 1/3 the cost of Jack's purple stuff.
The MSDS lists only a proprietary blend; however, the shipping classification UN 3265 and (1-Hydroxyethylidene diphosphonic Acid)
Start-up dosage: 15 oz. per 15,000 gallons. Maintenance dosage: 5 oz. per 15,000 gallons.

For pools with only minor issues with Iron, carefully monitoring PH and regularly adding a sequestering agent seems to be a cost effective solution.

I have also been watching the threads on the new product to the market CULator. While the convenience of this product would be a plus, the annual cost would be much higher than the regular use of a sequestering agent.

PSG