Uh oh... chlorinated water made it into the tank

[fishoholic]

Add some Prime (or whatever de-chlorinator you use) and keep a close eye on the water quality parameters. A 25% water change wouldn't hurt either. Shouldn't of killed off all your live rock by any means but it probably effected some of the beneficial bacteria that was starting to build up. You might notice your tank go through a bit of a cycle again.

3g in a 175g system isn't much so I wouldn't stress to much about it, just keep an eye on things and wait awhile longer before adding any fish or corals.