Does anyone know anything about gardening?

Is this the place for pond advice? We have a (no pump) pond which filled with rainwater over winter and now has newts + other wildlife in it. It's getting pretty low now and I'm trying to refill, but have exhausted water from our water butt - all that is left is

• the really murky water butt stuff that comes out if you tilt it - there's a fair amount of this but it smells grim. Suspect it may have the undisturbed run-off from tarred shed roof in it..
  
• fill it from the tap, wait 24 hrs for chlorine to dissipate (how well does this work?!) And then try to fill. Risk is that we can only do a couple of watering cans at a time, not sure if tap will change the water quality too much and will the water evaporate while standing waiting to go in?
  
  

Any thoughts what people would do...? Don't want to leave the newts homeless