nasty stain on bottom at opening

[mbar]

You can try rubbing vitamin C on it, or fill a sock with ph minus and rub the stain. If the stain comes off, it is a metal stain. If it doesn't it may be just staining from leaves, or acorns, or algae. If it is the latter, it will come off with the chlorine in the water. You can try rubbing a chlorine puck on it. If the stain doesn't come off with the chlorine, it may be algae under the liner.

[waterpro]

I had some pretty bad brown stains on my liner when I opened my pool this year (from leaves and other organic matter).....After shocking my pool twice and brushing it a little bit, there gone.......

[docsobeck]

thanks folks. you are correct. what a complete waste of panic! after a good shocking last night, the stain is pretty much gone this morning.