Safely adding rocks to your tank?

[doctorp]

I want to add some nice smooth round medium sized river rocks to my tank. I live next to a lake so I've got lots of rocks to choose from. What's the best/safest way to get these rocks ready to go in my aquarium without disturbing it too much?

 

[Jarred Darque]

I would simply boil the rocks for a little bit. other than that, they should be good to go.

 

[Fishyfanatic]

Be careful with boiling. I know there are a few types of rocks that explode when they are heated at too high of a temp. You could pour boiling water over them. If it were me, I'd soak them in a pretty high bleach solution then clean in hot water to ensure the bleach is completly removed.

 

[SeanMurphy]

You'd be hard pressed to explode rocks by boiling them. Crack them, maybe, but not violently explode.

If you baked them in a 400-500'F degree oven, they might explode, but otherwise, unlikely. Exploding rocks occur when the water inside them is heated past 100'C, and it boils, which creates steam, which, if it can't escape, will cause the rock to explode. Potatoes will do the same thing. You'd be hard pressed to explode a potato by boiling it, but if you bake one without stabbing it to give the steam a release vent, they'll explode pretty regularly.

Boiling the rocks would only expose them to temperatures at (or very slightly above) the boiling point, and it would take hours for the inside of the rock to reach that temperature, as rock is a very poor conductor of heat. Boiling them for 10-15 minutes would be perfectly safe, as long as you're on the lookout for normal boiling hazards (splashes, boilovers, dropping the pot on yourself).

The problem with soaking them in bleach is that many rocks (granite, limestone, etc) are very porous, and will soak up the solution they're in, osmosis drawing the water out of the rock and the bleach solution in. If left to soak for a long time, this will permeate the rock and then when placed in the fresh water of your aquarium, will leach the bleach solution back into your tank water over a period of many days, causing chlorine spikes and requiring addition of dechlorinators.

I'd recommend a 20-30 second bleach DIP, at most. This is around the time that is used in home brewing kits to sterilize relatively clean items for use, so it should be enough to kill any microbial beasties on the rock's surface, as long as it's been scrubbed free of plant material, etc.

As long as the rock LOOKS clean, however, it probably is. A rock that's been scrubbed, and allowed to air dry in the sun on a hot day is probably as sterile as it needs to be. Your tank is not a laboratory sterile environment, remember. Your tank additions need to be clean, but being sterile makes little sense, since the top of the water column is open to whatever you have floating around your house every day. And trust me, that's a horrible, airborne soup that your fish (and you dogs and your kids and yourself) are exposed to. Viruses, microbes, bacteria, mites, dust (which is mostly what mites excrete after feasting on your dead skin cells), you name it, its probably already in your air and therefor, in your tank.

Happy breathing

 

[BillD]

I use bleach all the time for anything that goes into my tanks, and have no problems. Bleach is not that persistant and can be rinsed off or soaked off. If you are really concerned, you can soak them in water with dechlor, or a little vinegar. A 20 to 30 second dip will not do it. A bleach solution will pretty much kill/oxidize any organic material on the rocks, making it pretty much sterile. The rocks I use are all from Lake Ontario, and are a variety of types, including slate and granite, and all have been treated this way, without incident. As far as the air above your tank being a source of all sorts of organic and other pollutants, it is, but no fish parasites.

 

[SeanMurphy]

Any aquatic parasites would just as easily be killed by leaving the rocks to dry for a couple days, as a soaking in bleach. And like I said, its not the bleach on the surface of the rocks that's the problem, its what was absorbed into the rock. If you do a soak, then as long as you soak for at least that long in a fresh water soak, it would be fine. Boiling is still preferrable, unless the rocks are too big or there's too many. The fewer chemicals in your tank, the less problems you'll have in the long run.

Its not the fish that I'd be concerned about with the bleach in the water. They can handle a little chlorine without a problem. Its the unjacketed nitrogen fixing bacterial in your filter that'll take the hit, causing ammonia spikes.

 

[Fishyfanatic]

I've never witnessed a rock explode but I have heard that it can happen to certain rocks if boiled. I don't remember the specifics of it though. The topic was brought up in a thread a year ago or so.

I'd go with the bleach method though.

 

[Zagz]

I bleach rocks and then soak in a mixture of water and dechlorinator to be safe.

 

[Nell]

One other thing that no one mentioned is that you need to test the rocks to make sure they are inert. Certain types of rock (such as limestone, dolomite, etc) will slowly dissolve and raise pH in the tank, sometimes to dangerous levels.

There are a few ways of testing this:
1. Drop a little bit of white vinegar or Muriatic acid onto several places on the rock. Wait a few seconds, and if it bubbles at all, the rock is not safe to use. Using vinegar is not guaranteed accurate since it is pretty weak.
or
2. Leave the rocks sit in a bucket of the same water you use for your tank. Also fill up another container of water without anything in it and let that sit too. Let them sit for several days to a week, then test the pH of both. If there is a difference in pH, one or more of your rocks are not safe to use.

Don't skip this step.
I learned the hard way about this when I added sand that had not been tested to a tank. I ended up with a pH over 8.0 and lost several fish before I realized what was going on.

 

[DrizzleWizzle]

Whenever I've heard about rocks exploding during boiling, it has been in reference to pumice, lava rock, or another visibly porous rock. The idea is that these rocks might have trapped gas pockets inside, and, when boiled, those gases heat, expand, and cause the rock to explode. From what I've read, the worry is NOT that the water inside the rock would boil.

That said, I've never experienced an exploding rock myself. I can only vouch for what I've read, not that I've personally seen it. But better safe than sorry, and blah blah blah.

 

[Sidi]

I've had an exploding rock nearly nail me in the face (it screamed right past) as a kid, but that was in a fire. It's not hard to find river rocks that explode as you heat them.

But I doubt it would happen with a short time boiling. And if it did, there wouldn't be a problem if you weren't in splashing distance.

 

[M@]

I teach a soil mechanics lab and we boil sand all the time to find the specific gravity. The sand explodes like crazy. Even before the water has reached the boiling point. I think this is due to the temp at the bottom of the pycnometer being higher then the water its self.