islandwahine,
Bike is an island enviroment, hmmmmm cool nights hot days, expansion & contraction in a humid climate equals condensation in the tank.
Water sinks so check for leaks (moist spots) on lowest spots first. Toilet Paper works great for checking for
tiny wet spots, then it can be put in a can (cat food, metal coffee, etc etc) and burned.
I have used a product called POR15 (
http://www.por15.com/ ) to seal some old tanks I had. A little expensive but it's tough as bullets. They do make a full tank teartment system. Don't get it on you hands, it sticks......long time.