On the acrylic overflows try this. Put a couple towels down on the floor or table and lay the tank on it's back side. Then lay vinegar soaked rags on the overflows. You can pour a little extra down occasionally too. After 15-20 minutes the vinegar will have loosened up a good bit of the coraline which can be gentally scraped off with the plastic scraper. Repeat till you're satisfied.
On a side note I'm planning on getting some citric acid linked above to do this as well as to clean pumps & heaters.