i will be starting a chilled aquaria here in San Francisco California,
cooling the water down to 55-60F to keep local invertebrate species. can
you all suggest any web pages or usenet groups that focus on such systems?

Not off hand, but I'm sure there are some out there, can be every bit as
spectacular as tropical reefs.

also, do general water chemistry tests such as nitrate, work at chilled
temps,

yep, with a few exceptions. SG is obviously different but the set I bought
(LaMotte) works on both tropical & temperate tanks so I'd think most others
would as well.

James