Bleach or vinegar might also work. Curing rock all depends on how much organics are left on your batch of rocks. You can put it in a rubber maid with heater and power head without doing anything but you will do to test your phosphate level until it reaches your prescribed optimum level. It could take up to a few month before you reach 0.02-0.05 ppm. Again, it all depends on the amount of water changes and phosphate removing agents you are using.

I did another 3 hour acid bath for my rocks.

It did a much better job, but still left a bunch of dark brown crap on the rocks. The water it came out of was nasty, so although I still have stuff on my rocks I know a lot of it is now gonzo!

Nice dude!

What's the suggested bath time ? Does it depend on the amount of rock ?

From what I have gathered, 2-3 hours is pretty decent for an acid bath.

Remember that these rocks aren't necessarily pure calcium carbonate - there's probably plenty of mineral contaminates in the rock that were either laid down by the corals themselves, or precipitated out through various chemical processes after the corals that built the rock died trapped within them.

A little discolouration at the end of the whole process wouldn't surprise me in the least, and you might need to dissolve the entire rock to truly get it all out.

In 40-50 gallons water how much bleach should I put in ? Thanks

Add 1 part bleach to 10 parts water. Same ratio for acid. Always add chemical to water, not the other way around.