I have an 18 inch perc with an ice catcher, which I regularly fill with ice, and in the bore there's a lot of water spots, it's unattractive! What should I use to get rid of em?
Yes, Iso is great but simple green gives it a bran new glass look, gets rid of all water stains, when you clean your bong with hot water (I usually do after every couple sessions) but after rinse it with cold water, this well help reduce water stains!
The spots are most likely from hard water and the ice you are using. Clean it well using SG and then try using ice made with water from a britta filter, or get a bag of ice from a store and that stuff is usually "clearer" and is less hard, which will leave less hard water stains on your tube.