Hi Carl;

Dichlor is dichlor, whether it's called "Pristine Blue Extra" or something else. It's just a form of chlorine combined with stabilizer (cyanuric acid).

Here're are the issues you are facing:
1. Last I checked -- and it's been several years -- you can't legally throw materials like Pristine Blue away. Among other things, it may still be the case that if you spill more than 10lbs or so of it on the ground, you have a federally mandated "Reportable Quantity" toxic release. (I'm basing this on the 5lb RQ level for undiluted copper sulfate -- I'm not at all sure why the RQ is so low for that; my recollection is that the RQ for industrial bleach was 1,000 lbs, but there are more than a few weirdities in environmental regulations.

2. Copper will control algae, and will kill most kinds, but it's pretty useless as a sanitizer (antibacterial / antiviral / anti-protozoan)

3. Copper alone can and does stain and turn blonde hair green -- but if you keep the pH low and the copper levels in range, the problems aren't too bad.

4. Copper AND an oxidizer (like chlorine) stains pretty badly.

5. Copper AND an oxidizer AND elevated pH (7.6 or higher) pretty much stains everything.

6. You can add metal sequestrants to the water, to prevent staining, but they reduce BOTH the tendency to stain AND the algicidal properties of copper.

The only options I know are to
a) clandestinely flush small quantities down your toilet, and get rid of it cheaply. (Don't do this if you have a septic tank; don't flush more than 1/2 cup at a time.)

b) use it in your pool WITH chlorine; ignore the stains, and warn blonde haired swimmers before they get in.

c) use it up over the next 3 - 5 years as a WINTERIZING chemical.