AG pump/filter question - have a lot of suction at the skimmer and return

Catching up on unposted photos - these two from bbink nicely show the color change in algae from successful shocking. The first shows the untreated algae; the second shows the algae a few hours after shocking. Please note that the tannish green color of the algae in the second photo is typical of injured, but not DEAD algae! If you stop treating at that stage, the algae can come back in hours!

Pre-shock:
https://lh3.googleusercontent.com/-K...eatment-ed.jpg

Post-shock:
https://lh5.googleusercontent.com/-n...g_shock-ed.jpg