I have used a weak solution of muriatic acid with great results. It does not take long and the rocks will come out looking like the dry rock you started your new tank with.
I have a pretty bad vermited snail problem in my 210, so I wanted to see how well an acid bath would work to clean a few rocks of the snails. It worked perfectly.
My rock is pretty dense though, I got it from Reef CLeaners out of Florida.
I used about a quart of muriatic acid I bought at Home Depot in a 5 gallon bucket of RO water. This works out to be about 5% acid. I got a slight bubble action but nothing that would foam up over the top of the bucket. I let them soak in the acid bath for only about an hour and that was long enough to dissolve the snail shells and clean the surface of the rocks.
After the rocks were clean, I added baking soda, rinsed the rock with a high pressure garden hose really good, and put them in a bucket with new RO water and a powerhead for a few days.
I then let them dry out in the carport a few days and put them back in my tank.
Now I need to do the rest of them a few at a time a couple of months apart and hope the snails don't come back with a vengeance.
