as far as ich and transfer go... when you place you new tank. .. transfer rock,sand,water. this will begin to cycle again as you have the sand bed disturbed.... the other fish can then be treated in your 90g for ich however you would like (hypo,feedings,at a last resort copper) or you can get a new sandbed in the new tank... but the lifecycle is a month so wait two months to be sure before adding fish to new tank.
just a suggestion.