How can I clean these brown iron stains in my pot? I use a big aluminium pot to boil water. I think the water contains iron because after 4-6 months, the inside of the pot is full of brown stains. The colour is just like ferric.  There are lots of circular brown areas (1-4mm diameter) in the pot. 


Is this stain caused by the iron in the water? If not, what is the
cause?
How can I remove these stains?
Can I do anything to prevent these stains in the future?


Pictures
If it's rust stains or other kinds of scale build up, CLR will take care of it: 

http://www.jelmar.com/CLRbasic.htm

From the pictures (thanks for adding) it looks like sediment from the water (source, pipes, etc) and CLR cleans it easily.  Just don't breath the fumes.

Also, you can try commercial coffee pot cleaners such as http://www.urnex.com/ to remove the build up. 

Finally, if none of the above is available in your area, try Vinegar first.  If that didn't work, wash off and switch to baking soda.  you may have to make a paste and let it treat for a while.

There is also this recipe for cleaning rust stains from aluminum pots, though I haven't tried it.