If you can, start by getting the tank stripped down and cleaned out first. (Mine's a small tank though, so I could haul it to the bathtub.) Once you know it's good, you can place the objects (like your rocks) in it and observe.
I soaked my cave rock and my plants, and even my driftwood (most people thought that would have been something to toss, but it made it), for days, while I went through the process.
After the tank itself is good, the tank filtration and plastic pieces (frame, etc), would be next. I could actually get to mine with my hands, tubing and all, and ran very hot water with the aquarium salt through it. It comes clean pretty fast, being plastic.
Soaking and rinsing those items in the very hot salty water did pretty much work for me and my plants/cave rocks, so I bet yours which had less exposure will be ok. You may just have to let it soak for a day or two, and rinse/scrub.
I had a checklist of things, so I was sure not to miss anything:
1. Tank
2. Tank filtration/equipment/plastic housings, etc.
3. Thermometer (really scrub on the soft plastic cups, etc.)
4. Ammonia Alert (these both were coated in the slime, but came noticeable clean fast.)
5. Heater - this one was a challenge, since it has little internal spaces. But I submerged it for some time, and rinsed for some time, etc. I didn't end up having any issues from it. Be pretty thorough... Don't forget to scrub substantially DOWN THE WIRING of the Heater and the Filtration, enough to wear it was under water. Along with any airline tubing you had.
6. Clay Pot
7. Rainbow Rock Cave
8. Plants (so keep in mind, everything not being tested has been soaking for some days now)
9. The last thing was the 2nd gravel attempt... which were white rocks (a nightmare even when they aren't contaminated to keep from being cloudy!) and I worked on every night for 2 weeks.
ALSO - go nuts about any screws, etc. There's a screw on the bottom of the granite base attached to my driftwood... I believe in the end that was the cause of the 2nd failed attempt, and the resudsing of the tank. Just a slight amount of the white goo had attached to the side of the screw, and when the water hit it, it just spread.
Once they were in, and it ran clear, I knew I was finally home free. The whole process took me about a week to undo it, and about an additional $65. I fishless cycled using fish food (I was scared of ammonia after all this!!!) for about a week, before deciding to redo the aquascaping yet AGAIN *lol* and change out for black rocks. (I did leave some of the white in, to keep the bacteria that had already started developing.) So really, all the work I spent trying to "save" the white rocks was a waste in the end... but it was a learning process.
Originally I intended to put guppies in the tank first, as sort of canaries to truly make sure everything would be ok for the fragile guys I intended to put in there (gouramis/neons/otos.) But as my new fishless cycle (which was back to the RIGHT kind of ammonia - fish food is too messy!!) went on, and I never saw any indications of soap etc., I felt a little more confident in my setup.
I believe in the end, my 30-40 hours of labor and thoroughness worked... because a week ago I put in my new fish, a dwarf gourami (which I'm hoping didn't bring something), 6 neons, and 3 otos. Other than the pre-injured neon, everyone has grown - everyone has nice round bellies. Everyone has beautiful color, and they eat very well. Everyone seems happy. That seems good enough to me, to indicate that I saved the setup after all.
I know you felt like a failure... I really know. The second attempt that failed was so distressing to me, that I got sick over it the next day and called in sick to work - I just couldn't even sleep over it. Unfortunately, some times we don't learn the information we need from the Internet, (no one had ever mentioned Surfactants on my site, just perfumes.) You THINK you're doing everything right... and you contaminate everything you've bought. That's why I went at it with one item at a time, so I could feel at least a little bit of hope.
The forum I had been visiting told me THEY would NEVER put fish in something that had been previously contaminated. I've never felt like I could go back there, because unfortunately I didn't have another $300 with which to buy EVERYTHING all over again, just in case. But I feel my trial method, and replacing key items (like gravel and bio wheel/filter media) in the end worked. (Unfortunately, the constantly washing and replacing the gravel did do a number on the lower inches of my acrylic tank, and I did get some scratches moving it into the bathtub. Probably some day I'll replace the tank in the future.)
In the back of my mind, I worry right now... I'm hoping that I didn't miss anything, that would mean that maybe they wouldn't DIE... but would maybe be prone to illness/stress, etc. I'll probably never know for 100% if it is perfect, but then again, many people's fish do come down with illnesses, regardless of issues like mine.
Right now, I guess I should feel happy that everyone is growing, and looks beautiful, and seems very happy, with no signs of stress. I guess I've done what I can.
I used to think that I failed... but I try not to think that way anymore, because in the end, at least thus far, NO fish had died at any point. They simply weren't there to experience the problems. (And my hands were really soft by the end of the week. *lol*) I think EVERYBODY makes mistakes - but a lot of times they end up inadvertantly hurting their livestock. At least we have that advantage.
The fact that yours was in there for such a short amount of time before you caught it, I think you'll be just fine. If I did it, after almost 2 weeks, you'll probably do real well.
If I didn't answer your questions directly, give me another holler.
