For now, I'd say deal with the algae and then worry about adding more CYA after that. You need to shock your pool. Any reading below 30ppm will not be detected on the CYA test so you can't assume that you have 0 but rather have to assume for now that you may have almost 30ppm. Go ahead and shock the pool up to around 15ppm. You can't shock a pool with trichlor tabs. Might want to use bleach as your source of chlorine to shock with. Do you have Walmarts in your area? Each of the 121-oz jugs of their generic 8.25% bleach will add about 2.8ppm of chlorine. You can use that as a reference to help you figure out doses of bleach to add whenever you test.

A couple of links that will help:>
http://pool9.net/cl-cya/
http://pool9.net/tk/ (Not sure if you can ship this kit to the Virgin Islands or not?)
http://pool9.net/oto-chart/

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