Mildew inside lava rock?

[musicman]

About two nights ago went over to my tank in progress and realized that it was putting off an offensive odor. I did some brief investigating and discovered that my lava rock was stinky. I smelled it in several different places and got an equal number of different smells. In general I found the faint smell of musk and mildew.

Six days ago, when I first got the rock I hadn't noticed any smell. The rock even looked rather clean. I rinsed it anyways, for good measure. Afterwords, I soaked the rock in a 5 gallon bucket. When I put the lava rock into the water in bubbled and fizzed letting off air trapped in the rock. I realized that the holes in the outside of the rock went through its entire internal structure. It was like a heavy, stiff sponge.

A sponge indeed. When I removed the rock from the bucket about two days later it bled water. I put it on a towel where it continued to let off more water until the chair underneath the towel was wet. I shook the rock out and it appeared to be empty so I found a suitable placement in the tank.

It let off more water while inside the tank! I soaked it up with a paper towel and didn't think much more of it after that. That is until now. I figure that there is still water inside of the lava rock. That moisture inside of a dark warm rock would make a fantastic environment to grow mildew. Well crap. I wanted to put that rock in my tank.

I took the rock outside and left in on the table on our back patio. It's supposed to be over 100 F for several days in a row. If anything, it should help dry out the rock. But I am afraid of what problems I could introduce to the tank when I allow the rock to get wet again.

What can I do to make this lava rock safe?

[happygirl65]

That is a tough one.....since it will soak up whatever you put it in.
You could use hydrogen peroxide, that should kill mildew....and will breakdown to a harmless substance. Soak it in your bucket with hydrogen peroxide full strength would be best (from the grocery store or walmart, not an industrial supply) Where did this rock come from?

You could also try boiling it. Put it in a tub and keep pouring boiling water over it, that would surely kill anything. The trick will be keeping the water hot enough to get that boiling water all the way through it.

[musicman]

The rock came from a saltwater aquarium store.

I like the idea of hydrogen peroxide. It seems safe.

My girlfriend thinks there are safety issues involved in boiling or baking a piece of lava rock. Its full of space and she suggests that the expansion of gas inside of the lava rock could cause it to explode. It sounds plausible.

[happygirl65]

Well the source explains why there are smells coming from it....it was likely previously live rock so there could be all kind of critters inside the rock that have long since died.

You might have a long road of soaking it and changing the water until you don't have any more smells coming off of it. The peroxide dip couldn't hurt and I would at least keep soaking it for a few more weeks with frequent water changes. Eventually all the trapped particles etc will completely decompose and then it will be ready to use. Then you will have a cool rock all full of the benficial bacteria you need.
Best wishes to you, I am sure it will be a really cool looking piece when you are done with it.

[Zakk]

Musicman,

dont "boil" in the literal sense. you could run the stone under a hotwater tap for a couple of hours in the tub.

[meegosh]

You are correct musicman, you could end up with an exploding rock if you boil the rock in a pot of water. What you want to do is what happygirl said, keep pouring boiling water over the rock. You could probably use a diluted bleach solution to kill any bacteria in the crevices. It would be cheaper than peroxide and you may have some already. You can then rinse it thoroughly and then soak it in a bucket with some dechlorinator in it.

[musicman]

How will I know when the rock has been made safe?

[happygirl65]

Since the main issue is the organic material trapped inside the rock itself, I would say your best bet may be to soak the rock in fresh water and test it every few days for ammonia, nitrite and nitrate the same way you would watch to see how the cycle is coming along in your tank. Once the rock is fully cured you should see no more ammonia or nitrite and your nitrates will go up. By then you shouldn't smell anything foul anymore, just an "earthy" smell.
Even if you give it a bath in bleach, it will kill bacteria and mold if there is any, but it will not remove the organics. So you have to decide which method makes the most sense to you (Boiling water bath, bleach, peroxide as your initial attack to kill any bacteria and/or mold then soak it and watch for the levels to spike telling you whether there is still organics decomposing or not.)

[musicman]

Ok, will do. Thanks for all the help.

[FishEggs]

Why not just cycle it like live rock? any organics inside of it would break down and beneficial bacteria would colonize it.