# [UPDATED] Rocks Fizzing - still safe?



## Jester946 (Mar 30, 2013)

Fill bucket with water, test PH, KH, and GH, log results. 

Put rocks in water, let sit over night. test PH, KH, and GH.


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## flight50 (Apr 17, 2012)

Test with muriatic acid instead. Stronger than vinegar. What ever you do, don't boil it though. Bake it or run the boiled water over it. Test as Jester stated. I would extend the testing for several weeks though. Overnight may not be good enough. The don't look like lava rocks though. They look closer to petrified wood than lava rocks but that guess could be off.


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## jaekwong (Jul 8, 2013)

I've done just what Jester stated, will be testing the pH. Whats wrong with boiling - exploding rock?



flight50 said:


> Test with muriatic acid instead. Stronger than vinegar. What ever you do, don't boil it though. Bake it or run the boiled water over it. Test as Jester stated. I would extend the testing for several weeks though. Overnight may not be good enough. The don't look like lava rocks though. They look closer to petrified wood than lava rocks but that guess could be off.


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## djjcoleman (Jul 6, 2013)

jaekwong said:


> Whats wrong with boiling - exploding rock?


Explode? Not likely. It is used for some pretty heavy duty cleaning of concrete/stone/brick. See handling precautions here. http://www.naturalhandyman.com/iip/infxtra/infmur.html I would still treat the chemical with respect even at low concentrations. Better safe....


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## ckraft (Feb 19, 2013)

Vancouver? Probably a lot of rain, not likely to have pure limestone there. You may just have lime surface contamination of the rocks. Soaking them in a mild acid solution should get rid of that. American vinegar is a bit weak already, apparently it's different other places. If you are comfortable with acid, a dilute solution of hydrochloric acid would be my choice, otherwise pure vinegar for a week of so. The tetras will care, the mollies like very hard water, so even if it were limestone I suspect they would be okay.


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## Xiaozhuang (Feb 15, 2012)

If you run strong CO2, the rocks will leech faster/raise kh faster, so just soaking in water and testing said water will not mirror your tanks conditions. If it raises kh slightly over a long period, water changes will negate its effect. However if kh rises alot over a short period, then it destabilizes your tank conditions. If you're not keeping sensitive fish/plants, keeping a slightly elevated kh is alright.


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## lochaber (Jan 23, 2012)

I'm pretty sure at least a couple of those are limestone - the weathering pattern is pretty distinctive.

as most of the people already pointed out, using a stronger acid is better. The vinegar test is easy and handy, but it's not very reliable. Some carbonates (notably dolomite) are very reluctant to visibly react with acid, sometimes the acid may be too dilute to visibly effervesce (fizz), or the rock may have a 'rind' on it from weathering. In addition to using a stronger acid, scratching the rock a bit where you test it can help (also, if you can't scratch the rock with steel, it's probably safe).

And just because it does fizz doesn't mean you can't use it in a tank - most of those rocks they use in the Amano-style tanks are some sort of weathered limestone (that's why it looks so cool). It depends somewhat on what your tap water is like, what you have in the tank, and how often you do water changes (probably the most important factor) - if you do fairly large, frequent water changes, it may not be an issue.

In addition to watching the pH, keep an eye on hardness (both general and carbonate), as those will likely go up as well (I believe it's the elevated hardness that leads to the elevated pH). oh- and makesure you get a decent baseline - let some water sit overnight and then test it, some of the parameters will change slightly just by sitting out over night. depending on how much you like testing your water, I'd only bother testing it every couple of days, or maybe even every week. - just try and do something to minimize evaporation.

As to prepping the rocks, I'd just give them a decent scrub with a stiff-bristeled bursh,, and go ahead and put them in the tank. You can boil them if you want, although I don't think there is much point to it. There is a chance the rock may split/crack, especially if you heat/cool it rapidly, but if you put it in a pot of room temp water, bring to a boil, and then let cool in the pot, it will probably be fine. I've never heard a first or even secondhand account of a rock actually exploding from boiling, and I think this fear is just from people extending the 'don't bake rocks in the oven' bit to 'don't heat rocks'.


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## lochaber (Jan 23, 2012)

I'm fairly certain that most of those rocks in the picture are limestone. Limestone is pretty much entirely (aside from a few impurities, etc.) CaCO3. When hydrochloric acid (HCl) is added to this, you end up with CaCl2, H2O, and CO2 (this is what causes the effervescence).

CaCO3 + 2 HCl --------> CaCl2 + H2O +CO2

As far as using acid to completely remove the lime, this would only work for a rock that has a small amount on the surface, like say a chunk of granite or basalt that was sitting around someplace where carbonates were deposited on/built up on it. As to limestone, dolomite, etc., these rocks are effectively made of lime - Soaking it in acid will just further weather, and eventually completely dissolve the rock.

If you plan on doing large, frequent water changes, or if you plan on stocking fish that do fine at a higher pH/hardness, then these rocks will probably be fine. If you want to stick to tropicals that need softer/more acid water, and you want to be a little more lax about your water changes, you should probably skip these rocks. You might be able to coat them with some epoxy or something, but I think that would be more trouble then it is worth, and may not look very good. (in addition to making it harder for plants to grow on the rocks).


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## flight50 (Apr 17, 2012)

jaekwong said:


> I've done just what Jester stated, will be testing the pH. Whats wrong with boiling - exploding rock?


Correct. Some rocks are more porous than others. Water can get trapped that will turn into vapor. What ever goes in must come put. In this cause it will be a build up of vapor trying to escape. If it can't escape, there is only one way out once is build enough pressure. 

He is an article I remember from awhile back on another forum I am on. Check it out. http://www.tropicalfishkeeping.com/beginner-freshwater-aquarium/do-not-boil-rocks-7424/

Whether is 100% accurate or not, I don't think anyone will really want to find out if they are near it so why tempt fate.


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## flight50 (Apr 17, 2012)

To add to that, I just remembered something. I was cleaning some recently acquired sandstone rocks I purchase from a lfs a couple of weekends ago and while I gave it a 10-15 minute bleach soak, I noticed there were several areas where around the rock that released a constant bubble stream There was either air trapped in the rock or water made its was in and was pushing the air out. Either way, if I had boiled this rock, I can easily see this rock giving way especially with its softer nature compared to igneous rocks.


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## lochaber (Jan 23, 2012)

I'm highly skeptical of the bit about boiling rocks exploding. I've never heard of a first hand or second hand account of rocks exploding when boiled.

I think it comes from misunderstanding the warning not to bake rocks or stick them in a fire. And even this is okay to do if you know your rocks - many of the older bushcraft and survival skills rely on putting rocks in a fire for various reasons (boiling water in a wooden/leather container, heating the ground for a bed, making cooking stoves, etc.)

The reason for the warning is that some rocks (typically sedimentary) may have water in them, and when you put them in a fire/bake them, the rock heats to the point where the liquid water turns to steam (roughly a 1000 fold increase in volume/pressure), and this is what causes the rocks to split violently and 'explode'. 

While boiling a rock may cause some cracking or splitting due to thermal expansion/contraction, it will not be anywhere near as violent, and you may not even notice it until you remove the rock. The best way to avoid this is to slowly heat the rock prior to boiling (just sticking it in room temp water, and then boiling that will probably work), and let it slowly cool afterwards (just let it sit in the pot with the water and cool). Pouring boiling water over a rock is more likely to cause it to fracture/split then actually boiling it.

As to air pockets in the rock, the difference twixt room temp and boiling will only cause something like a doubling of pressure/volume, which I don't think would be enough for the rock to explode (maybe split, on a really weak rock, but I think even that is unlikely). Think about eggs - they have a very thin shell, and often times have a quite large air pocket in them, yet I've never had an egg explode from boiling. Putting it in the microwave is a different matter. 

Sorry, this is something that's been bugging me, I think it's unwarranted fear-mongering borne of overdoing the safety warnings bit, and it bugs me when I see it spread around.

That said, don't bake rocks, that's the case where there is a risk of explosion. Boiling should be fine, however I don't really think there is much reason for it. -a soak and scrub with a brush should suffice.


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## flight50 (Apr 17, 2012)

I would prefer baking over boiling. If baked, the water will evaporate if there is water inside. Hardly any pressure there following up behind the vacated water. Chances are water would have already vacated the rock if it wasn't taken from being submerged in water. If a rock is boiled, the cavity in which water vacated will constantly be replenished by already high tempt water. An egg is something totally different. Its not a solid mass thru out. When an egg over cooks it just cracks or splits open. Nothing that would remotely kill anything. The vast majority of us aren't rock experts so knowing the makeup about one is unknow. To each is own but I stop taking chances with boiling rocks along time ago. Many will continue to boil them and more than likely get away with it as I and many others have in the past, I just don't gamble with the thought anymore.


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## lochaber (Jan 23, 2012)

agh...

Baking is what can cause a rock to explode (in rare cases). Water trapped in the interior (or a pocket, vesicle, whatever...) has the potential to turn into steam, which will exert much more pressure on the rock then a heated pocket of air.

1 mol of liquid H2O is approximately ~18 grams, with a volume of approximate 18 ml at room temp/pressure. That same amount of water in gaseous form will take up about ~22litres at room temp/pressure, which is about a 1000fold increase in volume (or, if you are trying to keep it in the same volume, a 1000x increase in pressure)

for an air pocket of about the same starting size ~20ml, raising the temp from room (~278 kelvin) to boiling (~373 kelvin), will cause it to expand to approximately 27 ml, or about a ~34% increase in pressure for the same space. (p1*V1)/T1 = (p2*V2)/T2
It's really unlikely that such a small increase in pressure will cause.

A pocket of water in the rock isn't really going to do anything if you boil the rock, as the temp will sit right at 100C as long as there is water in there, and it would take a very minor increase of pressure (either from heat expansion, or a miniscule portion of that water converting to steam) would drive the boiling point over 100C, meaning that pocket will not continue to boil/convert to steam.

I still feel that any chance of danger from boiling a rock is so small as to be insignificant. Baking it however, does pose a significant risk for rocks to explode (even then, would be fairly rare, but it's possible). -Probably won't hurt anyone, but may damage the oven.

I understand the concerns about safety, and it's good to take those things into consideration, but in this case, misinformation is causing people to do something in a more dangerous manner. I really don't think there is any need to boil rocks, but if you are concerned about sterilizing it, and don't want to use chemicals, then boiling is probably the safest way.


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## jaekwong (Jul 8, 2013)

So an update: After completely soaking the stone in water and testing the pH the first day - I have tested the pH level again today - 4 days later.

On Sunday: pH 7.2
Thursday evening: I used the first kit but it maxed out at the pH so i used the high pH test kit and came out with a reading of pH 7.8

So my question is, is this safe to use? It's a bit on the basic side...


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## flight50 (Apr 17, 2012)

Most rocks will be safe in theory. Remember just because it fizzes doesn't mean its not safe. It more of less means it will alter you water parameter(s). The true question is, how much swing in ph are you comfortable with allowing. You can add some driftwood or more driftwood, depending on what you have, to add more acidity. It would counter balance or at least slow down the rising ph. You have to find your happy medium. The lower the ph you start with, the less alkaline your ph will be in the end. 

For example, my tap is 8.0. I have some med size pieces of driftwood cramped into a 29g that all use to be in my 55g. Being in such a small tank, I have less water to dilute in my 29g vs my 55g. I use to run 1:2 R/O & tap with co2 24/7 for my 55g and got ph6.8 all day long. I did the same for my 29g(emergency tank when 55g lost a seal) when I transferred everything over. Low and behold, my ph kicked down very very low without even apply co2. I sit at ph6.0 or lower. By using tap, I can raise the ph but I have to find that medium before the ph drops and its all controlled via water changes and the frequency I do them.


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## jaekwong (Jul 8, 2013)

So you're saying find ways to lower the pH. I recall c02 can lower the pH in a tank, and haven't ran the tank with c02 just yet. i just left the rocks in still water in a covered bucket. 

do you think c02 could do the magic and lower the pH in general making it habitable for plants and tetras?



flight50 said:


> Most rocks will be safe in theory. Remember just because it fizzes doesn't mean its not safe. It more of less means it will alter you water parameter(s). The true question is, how much swing in ph are you comfortable with allowing. You can add some driftwood or more driftwood, depending on what you have, to add more acidity. It would counter balance or at least slow down the rising ph. You have to find your happy medium. The lower the ph you start with, the less alkaline your ph will be in the end.
> 
> For example, my tap is 8.0. I have some med size pieces of driftwood cramped into a 29g that all use to be in my 55g. Being in such a small tank, I have less water to dilute in my 29g vs my 55g. I use to run 1:2 R/O & tap with co2 24/7 for my 55g and got ph6.8 all day long. I did the same for my 29g(emergency tank when 55g lost a seal) when I transferred everything over. Low and behold, my ph kicked down very very low without even apply co2. I sit at ph6.0 or lower. By using tap, I can raise the ph but I have to find that medium before the ph drops and its all controlled via water changes and the frequency I do them.


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## flight50 (Apr 17, 2012)

jaekwong said:


> So you're saying find ways to lower the pH. I recall c02 can lower the pH in a tank, and haven't ran the tank with c02 just yet. i just left the rocks in still water in a covered bucket.
> 
> do you think c02 could do the magic and lower the pH in general making it habitable for plants and tetras?


Sure CO2 has that magic. When I had my 55g that is the only way I got to 6.8. Driftwood alone didn't do it because I had alot more water for the tannins to spread thru. Between co2 and driftwood they are two of the most common and easiest. You have soils such as AS and peat that can do the trick as well.


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## Diana (Jan 14, 2010)

If the rocks are adding minerals to the water this is different from altering the pH, and of more concern. 

Set up a test bucket and test GH, KH and TDS (well, pH, too) for a week or more. 
If the changes you see are small, and within the range that is OK for the fish you are keeping, then go for it! 
Larger changes in the mineral levels is going to be harder on soft water fish each time you do a water change. That sort of rock is probably better placed in a hard water tank.


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## lochaber (Jan 23, 2012)

I think you are going to have to either find some inhabitants that are fine with somewhat elevated pH and hardness, or use some different rocks.

trying to lower the pH won't really work very well, because the minerals from the rocks (CaCO3), will be acting as a buffer - any time acid is added to the tank, it will react with whatever carbonates are dissolved in the water column, and eventually the rock itself.

The rock will dissolve, putting Calcium and Carbonate ions into the water column, raising your hardness. This, in turn, is what will cause the pH to rise, as all of the acids are exhausted by reacting with the carbonates. Adding acids will just cause pH swings, and faster weathering of the rock (but probably nothing a human would be able to visibly notice).

If you are really determined, you may be able to get a working tank, but it will probably involve frequent, heavy water changes. Take a look at some of the Amano-styled tanks, a lot of them use very similar rocks (weathered limestone), and see what they are doing.


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