Miri - Yup, there seem to be plenty of aquarium stores in the area!
I'll be the first to admit that I'm not up on all the chemical interactions, but I was able to find an article that addresses the relationship between alkalinity and pH. Hope you remember high school chemistry (and if you're in high school, you should take chemistry just to get this stuff down!):
http://www.advancedaquarist.com/issues/may2002/chem.htm
Like Brucey said, the swings in pH are the tough part for the animals. Here's another article on pH problems:
http://www.advancedaquarist.com/issu...e2002/chem.htm
Your pH might not be the problem, but it should be good to get it stable anyways.