depends on the type of rock, some need to get a good wash while other should be tested to see there effect on the water conditions, as some rocks can lower your PH substantially, so are you aware of the type of rocks that you've purchased? Usually you can set the Rock down in vinegar and if it fizzes then it is not safe for an aquarium, usually further tests are needed, I would advise that you place the rock in a bucket for 2 weeks, and test it regularly. if it changes the PH, and Hardness a lot then you shouldnt use it in your tank
if the rock is already confirmed as aquarium safe then just giving it a good, AQ salt dip,and wash it thoroughly in warm water then it should be okay to use in your aquarium
Last edited by fishy friend2; 03-10-2012 at 02:43 PM.