u can use the Paint programme in yr pc.
open the pic,then under the image tab,select stretch/skew. reduce pic to yr required size and save it.
alternatively,u can google for irfanview(freeware) on the net.
yah,wud agree that you remove the liverocks in stages.at the same time,to minimise disruption to yr water parameters,do u have a good nutrient export in place i.e a good skimmer to draw waste out before they can degrade.