Mike,
any number of conditions can create less than desirable water conditions.
brainstorming.....
What kind of fish? how many? what's your tap water like? How often are you having to change the water? Under-gravel filter? Is there gravel? Are you using the tank to brush your teeth in it?
I am sure you have done a google on tank maintenance, but without knowing your setup it is hard to address what could be causing the problem.
Additionally, feel free to email me if you want to respond off post. I wouldn't want to be part of locking down an inappropriate thread.
