MURIATIC ACID IS THE BOMB!!!!!
I've been breaking down my two 55 gallon tanks and I've got so much crap on the skimmers/powerheads/return pumps/etc that I needed something with some gusto to get all of the calcium-based critters off.
Scrubbing with a scrubby-pad is just tearing up the pad.
I filled a 5-gallon bucket with water, put the pumps, etc in, dumped in some muriatic acid and it looked like an alka-seltzer bath. Bubbles...bubbles...bubbles...
It dissolved the heck out of the calcium.
Just beware!!!! Do this outside. The fumes are brutal. Also, you need to figure out what to do with the acid bath when you're done. If you dump it down the driveway, it WILL dissolve a layer of concrete (albeit a thin one) and cause some serious trouble in your sewer systems. Don't dump it down the drain in your house, since there's a chance it could damage your plumbing.
The best way to get rid of the acid is to neutralize it by mixing a bucket of water and baking soda (or lime...like the kind you put on your lawn) and adding the acid to the new bucket in batches and wait for it to quit fizzing.
Remember....always add the acid to the "other" stuff....not the other way around (I'm not 100% sure why......that's just what I've always been told and I'm still around to put up posts on reefs.org....so it must be good advice).
I've got some more stuff to clean this weekend, so I'll try and make a post of my own showing the before and after pictures.
Thanks,
Eboman
P.S. Otherwise, a regular jug of white vinegar works fine...not nearly as well as the acid....but it should do the trick. I usually get the 1-gallon sized jug and keep it around for cleaning skimmers and stuff.