Anti-duck: Dollar store - cheap shiny helium balloons.

Stained plaster: no idea, sorry

Is it plain plaster or Diamond Brite? Raise the FC to 12% or so of the CYA level, hold it there and brush daily. It will fade soon to where it isn't seen anymore.

They don't like large inflatables usually. Next up is a sprinkler with a motion detector.

Scott

I think plain plaster.. has quartz (blue specs) in it but overall it is white..and now white with 4 poop stains! :-)

I've inserted a 2" PVC pipe into the pool over leaf stains, etc and poured chlorine shock powder down the tube so it falls onto the stain. Brush up after and hour or so and stain is usually gone. Turn off the pump so water is still.
Also have one of these "stain erasers" I use for stubborn marks.

Here is a link that might be useful: Stain Eraser