Originally Posted by bja
Look elsewhere, it's not from your aluminum pot.
If you think it is your pot, fill it with vinegar(like 1 part to 4waters I think) and let it sit. Or boil it with just water. This will create an oxide layer and you can rule the pot out. When cleaning, do not use an aggresive scratchy. That can remove the layer.
Back on topic. Just add to the end of the boil. Nothing to worry about. I like to soak mine in star an first. Makes it nice and shiney, and I like shiney things.