Hmm, yes that info is helpful... :?
So am I to assume that it's been pretty much as is for the past 2 years? If so, then I'm surprised by the low reading of your CA, as it looks like your sandbed is operating properly..and if it is operating properly, then you should be seeing it dissolve into the tank water from the lower PH in the lower anaerobic layer, and as a result raising your CA level. Is your test kit maybe stale? Regardless of that, you are having nutrients building up and feeding the hair and bubble algae. Do you blast your rocks? ...
See this thread for my previous experience.....
http://reefs.org/phpBB2/viewtopic.php?t=6997.
Any plans to upgrade your skimmer? You could probably get away with more frequent water changes, right after you stir up a bunch of detritus that may be accumulating in your rock pile. Maybe use a turkey baster and a siphon hose at the same time.
Hair algae is no fun.
Mitch