When wanting to clean things for the tank, I go with the professional health people who deal with this question everyday. They use chlorine to clean our water so I see no reason to fear using it. The only difference in our tap water and a bleach water soak is the dilution. They may use a teaspoon in fifty gallons while we may use a half cup. But that does remove and react with almost everything that we want removed. Reading about chlorine say that it reacts very easily with any organic. Wikipedia definition, "An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon", not the organic like used in organic foods. Since oil is certainly an organic compound, we can assume the chlorine will react with it. While there it will also clear any questions of bugs, virus, fungus and a long list of other things we might not want in the tank.
When we boil things that have oil on them, where does the oil go? It floats around on the top until cool and lands back on the item we boiled and it is still oil. So instead of oily rocks, you get rocks that have been boiled in oily water.
For removing the chlorine we can do it just like we do for our tap water. We can wait for it to gas off as it dries. We know it does that as we can smell it as we drink or go around a pool. Or if we are in a hurry we can dilute it by rinsing and then deal with it using a dechlor product like Prime, etc.
