100% vinegar for 1-2 hours and everything softens up so all you need is a toothbrush to get it off your powerheads. My Maxijets are 4-5 years old and I've been doing these cleanings since I've had them and no problems. I figure the saltwater that they sit in day after day is probably more harsh on them then a little vinegar! I take them apart as much as I can and let them sit (I don't run them). I rinse in freshwater, put them back together, let them run a minute or two in freshwater, then let them sit a while in the freshwater and change the water occasionally.