I've had silver killcoil reactions before that's why I no longer use one!
Green algae can also occur if your computer is in direct sunlight, it really doesn't matter what protection you use, over time sunlight can break down any coolant, no matter what they claim, it can still happen in direct sunlight.
So is your computer in direct sunlight any time of the day?
Are we talking the XSPC pump inside the reservoir?, if so you'll have to RMA it back to XSPC, if it is the problem!
With algae in the loop the pump could be stalled by clogged water blocks stopping flow, or a combination with the radiator as well, which could appear that the pump has stalled, the only way to know for sure, is inspect inside the water block or blocks if you are running more than just a CPU water block.
You'll have to clean everything, take the water block apart and clean it carefully with a vinegar solution, (If it is a Copper water block, do not use vinegar on a nickel plated water block use dish washing liquid like Dawn), rinse thoroughly and reassemble carefully, make sure the O-ring seals are properly seated in the grooves, tighten the screws with the same pressure you found them set to, tighten snug, but don't over tighten and strip the threads.
If the water block is clogged with algae it will completely stop the water flow, but that doesn't necessarily mean the pump is bad?
You'll have to diagnose this problem one step at a time, so check inside the water block and post what you find?
In this situation I would just replace the tubing altogether, unless you spent a chunk of money on expensive tubing, personally I just use the Walls brand from Home Depot or Lowes and buy it in bulk, it's cheaper that way.
Edit: I searched out some links on the net regarding those that have run into this and how they cleaned theirs, but some of their methods I would not do, so I'm not posting those links.
I will help you all I can with advice, but first discover if the water block is clogged?