The reason that you "occasionally get a light algae on the side of the pool" is because you're not keeping your chlorine levels high enough to compensate for your CYA level. With a CYA of 80, you need to keep your chlorine levels in the 5-10 range, and go up to 20 ppm when you shock. By letting the chlorine drop below 5, you're opening the door for the algae to come in.

This is the pitfall that most people don't understand about trichlor tabs. They are easy, fairly trouble free--until the stabilizer gets so high that the chlorine can't compensate, then they start having algae problems that they throw all kinds of stuff "at" to try to fix--such as phosphate remover--when all they really need to do is keep adequate chlorine levels. The chart at this link http://www.poolforum.com/pf2/showthread.php?t=365 will explain better where the chlorine levels need to be kept in relation to the CYA levels.

In order to clear the green, you need to shock your pool up to 20 ppm, and hold it there until the water clears, the algae is gone, and you don't lose any chlorine when testing at sundown and again at sunup. Keep the filter running 24/7 during the process, and brush the pool at least once a day. After those conditions are met, let your chlorine drift back down to the 5-10 range, but never below 5 ppm. I would also stop using the pucks, because your CYA is going to continue to rise as long as you use them, and when the CYA rises, so must your minimum chlorine.

Janet