others have also used Muratic Acid for extreme cases. but, i think the precaution needed is much greater with that. There was a recent post with Marc mentioning that if you search for "muratic".
If you are using vinegar, be sure to remove the rubber suction cups if you are soaking the holder too. Anytime I've use vinegar with the cups, they wind up being ruined. If you use muriatic, it works fine with the cups too. JME.
Doug
Actually, I think powerheads all equipment, look cool covered with coralline, as long as it is not clogging up the intake. The only place I don't want it is on the glass.
