What can I add to kill algae

Well, the tank is on the third floor, so I dont really want to fill it with water, when I move to a condo in another year I probably will.

Im going to try to get a couple plants that I could stick in the water and see what happens.

i really dont think its the tap water, I had the tank filled before with fish in it and I never got bad algae, certainly nothing nearly as bad as it is now.
 
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