morechoff,

My first question would be, "how much Cl did you put in 8 weeks ago"?

If I assume you use 1-2ppm daily in normal chlorine loss (most pools lose that or more) and you have not added in 50+ days and still have 5ppm or greater, you must've had a Cl level somewhere between 55 and 110!! (yeah, I can see why you would have no algae)

Secondly, "Why"?