And just as a footnote to Carl's post, some trichlor tabs contain copper, so make sure to check your active ingredient list before you buy them, if that's what you decide to use. If it says "dual acting", or has copper in the ingredient list, don't buy them--copper is the culprit that turns hair and nails green. There are still some out there that do not contain copper. They may be a little more expensive, but not if you catch them on sale. Besides, in the long run the "cheap comes out expensive" because copper is a real PITA to deal with once it gets in your pool in levels high enough to start staining.

That being said, Please post your water testing results, as Watermom suggested, and we can help you go from there.

Janet