Sorry, but I never saw a vitamin c gel tablet. I have only had the solid form, so I don't know how you would get the gel on the stain without going in and rubbing it on by hand. Yes, it is a beautiful day, and I was just out getting the pool ready for closing I hate closing - it means it's the end of the summer. Anyway, I would just get the sequesterer for now, or not even do anything - I have closed with stains, and opened stain free. I think it may be that the the ph gets low over the winter, and as the chlorine gets low, the stains lift off. So in my experience, I wouldn't worry much about it, because you don't need to put any extra money in at the end of the season, and the stain treatments make it hard to rebalance the water - so if you want to close in the next two weeks, I wouldn't worry about the stain for now. If it is bothering you, you can do the sequesterer - I would recommend metal magic, because it is supposed to turn any metals in the water to salts, so they can be filtered out. Jack's magic is a very good product also, but it just sequesters the metals, unless you use the stain treatment which is ascorbic acid, and that will take a while to rebalance after the treatment. You also can't shock the pool for 2 weeks after the treatment, so you won't be able to close right away. Let me know if you have any other questions.