That's a pure linear quat, that will make the water foamy and use up a bunch of chlorine.

But, will it help with algae? Honestly, I don't know. But my own experiments with linear quaternary ammonia products were never encouraging.

You can get polyquat pretty quickly from Amazon:
Proteam Polyquat 60
In the Swim Polyquat 60
Kem-Tek Polyquat 60
And, honestly, if you super-shock the pool and eliminate ALL algae before covering, you can usually avoid any problems in the spring if
  1. you use a waterproof, light-tight cover AND
  2. shock the pool IMMEDIATELY on un-covering the pool.

There's also a tactic you can use to eliminate algae if you have resistant algae:
  1. Go ahead and cover -- but do not CLOSE -- your pool.
  2. Open the cover on a corner or side, so it can 'vent'.
  3. Add chlorine to 25% - 40% of your CYA (stabilizer) level (ie, a CYA=100 ppm means a chlorine level of at least 25ppm), and keep it there for a week.

Usually, this will clear things up, since you aren't losing chlorine to sunlight. But, yoiu'll need a K2006 or equivalent, if you don't already have one, to determine and measure proper chlorine levels. You can uncover the pool enough to drop chlorine levels down to 10 - 15% before actually closing. But, without actually knowing your CYA levels, I can't offer any ideas about timing or the like.
K2006 @ Amazon.
Good luck!