Dead rock to live rock project

As usual things concerning me seem to be strange.....it's them - not me, of course.

So at work chatting about the new tank, and one of the ladies in the breakroom says "My son used to have a big tank, but he stopped looking after it so I told him to get rid of the fish and take the tank down."
About an hour later she noticed the fish gone. "What have you done with the fish?" (there were two)
"Oh well as it's snowing I thought the nicest thing to do would be to lay them in the snow, and they would just fall asleep, then die" (I told you this was a strange tale).
"What? I didn't mean to get rid of them straight away you fool." At which point he rushed out into the garden, in the snow, returning with one solid fish.
She asked "Where's the other one?"
Holding the frozen specimen he looked at her "The cats eating it under the tree."

The tank was soon dismantled. So I asked about the live rock, as you would. "Oh we put that around one of the flower beds I think."

Needless to say the look of horror on my face was sufficient, as she then asked "Why, could you use it?"

So two weeks later I got a call saying she had the rock in her car. WHOOT! There is about 50 lbs. I would estimate varying from about football size to baseball size.
I have a couple of the 17 G plastic garden tubs, and have to spread them between the two as there's to much for just one. Both tubs are now soaking the rock to start off the cleaning process after being blasted with the hose.
I plan on about 2 weeks of daily emptying, hosing, then soaking for another 24 hours before repeating.
Apart from removing all the sandy dirt I'm also thinking some fertilizer may have been used in the last couple of years of garden use, but I'll ask her about that.

I'm thinking that if I then put a bunch of the rock in a tank and fill it with RO water and a power head and leave it for a week, then test for anything I have tests for, I will have a better idea of where I stand, before considering putting it anywhere near any live rock.

Very close to the practice of "cooking" live rock in order to remove phosphates. Set up a rack on the bottom of your container so you can siphon off the debris that comes from the rock and be prepared for this to take longer than a week , sorry.

Be sure to ask the lady about any pesticides used around the rock. I'm not overly concerned about fertilizers but I don't know how you'd neutralize a good dose of malathion.

I've had them soaking for 3 days, so today I turned the buckets on their sides and blasted small bunches of rocks, and watched the sand come flowing out.
However, I've noticed that there is some very firm green on some of these rocks, which is probably from being outdoor. So that, plus the thought that if the tank had been ignored for a while, then there is the definite possibility of Aptasia or other nasty's still existing in some form, I'm thinking of bleaching them all.

My thinking being that any sea life that may return will be unwelcome, it should rid me of any land based mould/spores etc. and I can with peace of mind know where I'm starting from.
So I'm thinking 25% bleach 75% tap water, soak for 2 days, then rinse like mad. Next day 100% change of water, and repeat daily for a week.
Then soak in RO water for a couple of days, and find somewhere dry (no garage alas) to let them dry out.
Any thoughts/comments?

I've never tried this myself but I've seen lots of posts where people use diluted muriatic acid to soak the live rock in and I believe that removes phosphates and other things that soaking in water or bleach can't remove. After the acid bath then go through your regular "cooking" routine.

http://reefcentral.com/forums/showthread.php?t=1748423&highlight=muriatic+acid+to+clean+dead+rock

how much acid should we use?
From what I know, that thing is supper strong!

Jeez, I thought I was becoming the mad scientist with all my water tests, but now bubbling acid (Cackles), now how to dispose of the body?
I spoke to the lady, and she told me the rock was around a tree, so neither fertiliser nor weed-killer/pesticides have been used.

I boiled some smaller pieces, brain coral etc. For over an hour, rinse, then have them standing in filtered water, which I will test in a day or so, just to see if anything shows up on the tests.
The acid, though an interesting idea would be a headache, not only the disposal, but also where to carry out the process as I don't have a garage.

Anything is being done slowly as I don't need the rock immediately.