You know what I would do just to be a P.I.T.A. I would take pics of your tank with the stand open so yo can see the skimmer, get them enlarged, and made into signs.
Put them in your yard the day of the party facing their drive way so all the neighbors can see it, and wright on them "this is not a bong its a skimmer", and on the other
"I was not invited cause they think im a pot smoker" and on the next one
"whos the dumb ass now?"
I would be insulted, and want the neighbors to feel like an ass, so I would try to imbarrass them at their own party, and the neighbor will find out the truth at the same time.
you could get one of those microphones coaches use that make those load obscene noises.
Stand in you back yard, and play with it all night. Hey if they call the cops you could tell them its your alarm for your fish tank, and it wass alerting you of a major problem. hehe pour some of your green scud from your protien skimmer in thier pool the night before their party
omg I love this smilie it looks like my kid sometimes