School Shark

Hi all... I am really new to marine...recently I had put my Live Rocks into the tank, but the next day or two, it had white patches on some rocks. they are soft and when my hand rubs on the patches, the rock surface of that patch and the 'mould' sort of disintegrates and falls off... Anyone out there knows what is happening? how to prevent/cure?

Hihi...Sorry to do a second hijack... I am really new to marine. Just added LR into my 3 ft tank, got a EHIEM Model 2213 cannister filter and a Ocean Free 1000 Power head for my tank... I think they are rather insufficient for my 3 ft tank, but will it have any side effects? Today I realised that some of my LRs have patches resembling white moulds growing on them. When I used my hand to rub it, it sort of disintergrate and falls off. Why and How to prevent?