old live rock

That's a valid concern, but FTR, we've been bleaching rocks for as long as we've been using them in aquariums. Before that, stony corals were bleached to kill the animals and clean their skeletons for FO tank deco, so yes, it's safe.

 

Thanks

 

Bleach evaporates.

 

I've done the bleach thing and it worked. How necessary it is I have no idea.

 

Bleach kills, cleans, and sterilizes without leaving a harmful residue; as already stated, it evaporates. Necessity, however, will depend on each individual situation.

NOTE: ALWAYS ensure that you're using "Regular" liquid chlorine bleach. The chemicals used in "New" or "Improved" formulas, such as those designed for colors or certain fabrics, may leave a residue that can have negative effects in an aquarium.

 

How much should you use.