Aeration + muriatic lowers carbonate alkalinity; it has no effect on calcium levels.

As far as I know, the only two practical ways to lower CH (or TH) are by
(1) draining and refilling -- and this only works if your fill water is soft!
(2) lime softening to precipitate the calcium and then vacuum or filter it out.

You can see if lime softening will work for you, using the calcium bucket test:
http://www.poolforum.com/pf2/showthread.php?16992