I need to thank my fellow R2Rers for all the help. The Aussie may not come back (has anyone heard of acan polyps regenerating from mere shreds?) but it does not appear to be getting any worse, and my other corals, including the fiery depths acan, are acting normal again. I think I've got things back under control. Whew! I have to admit that when I saw that acan falling apart I started having some nasty flashbacks to a disaster I had with my 50g freshwater tank. Something was wrong with the tap water I added during a routine change, and by the time the tank was full my beloved fish were dying one after another at such a rate that I'm amazed I saved any of them. I even lost my favorite, a gold nugget plecostomus named Vegas. That night ripped me apart and it seems I may never be completely over it.
Thanks for helping me keep this from becoming another disaster, guys. :') I seriously freaked out, and I don't do that.
Upgrading can't come soon enough. Messing up the chemistry in a 20g tank is just too easy for my liking.
On another high note, my RODI unit works a treat and I'm slowly getting everything back under control in my other tanks, which got a little neglected while I had to buy water. I had to let my FO and freshwaters go in favor of protecting my reef. Everyone seems to have come through that period without noticeable harm, thankfully.