I have had very good results this year keeping the stains away. I had to do an ascorbic acid treatment at the beginning of the year, and since then I have not had a problem with staining. I have used proteams metal magic, and have been putting in a maintenance dose weekly. I also have been using a natural clarifier SeaKlear. I have been very careful to keep my ph below 7.4, and my alkalinity at 80. Except this last week it got away from me and my water got cloudy I also raised my cya to 50, and added calcium to keep the number around 170. So I am not sure of which one was the most important (probably the weekly dose of metal magic). I wouldn't worry too much about the small hole in the bottom, it is most likely cosmetic, but I can tell it bothers you - I will call my pool company tomorrow and see what it was they used to patch the underwater chips. It looked like a putty to me, but it was a long time ago and the old memory I will see what I can find out. Enjoy the summer and the pool Oh yeah, and if your pool is the same size as mine, you have more like 15,000 gals.