Thanks for the advice, I set up the tank without live rock, but may add it in time via my QT (without fish in of course.) I didn't find this excellent site before setting up so haven't gone down the best path initially (i.e. live rock, better skimmer, sump / refugium, no canister filter.) I was also concerned about the hitchhikers I might get with the live rock having read about mantis & pistol shrimps etc.
Note the point about SG - I'm increasing slowly by doing 10% weekly changes with 1.026 or thereabouts until I get to 1.024.
As long as the fish are healthy and parameters stay good I'll migrate gradually to the better set up in time. Just to ask one part of my original question again - do I need to monitor/add calcium for the shrimps?
Thanks again.