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Testing Rock and driftwood

5504 Views 15 Replies 5 Participants Last post by  able_ranui
I have a rock and piece of driftwood that I have in a tank with a few guppies to see if they are safe. How long should I wait before transferring them to the show tank?
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From what I've read, the best thing to do in reguards to rocks is, before putting them in the tank, to take a knife or other sharp implement and to scratch the surface a bit then to pour a week acid on it. Vinegar is the most common one available (unless your a chem major or something fun like that). If it fizzes then it's not a good choice for your tanks (fish wise anyway...not sure on plants *shrug*).

As for the wood...if it's a store bought piece and you've had it in the tank for awhile I'd say it's good to go...personally I've collected all my pieces and boil/bake the smaller pieces to steralize then soak, soak, soak, in hot water before putting them in the tanks to release the tannins (and make it sink faster :wink: ). I have still noticed some lovely fluffy white growth on a few pieces but have been told that is natural especially when it's a collected piecs. The latest addition is to (dare I say it on this board) an as of now unplanted tank, it's been in for two weeks (still floating :roll: after bleach and 3 days hot water :roll:). So far it's still pretty clean as to "growths" but they may still pop up, although I hope they don't as this is one of the tanks I take care of for the office ([-o<).

Not super helpful...but just some experiences...


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Ok, if it fizzes it is bad because it leaches....what? I haven't tested this rock, but it has been 2 days and the guppies are still fine. ask for advice, and you challenge it? I mean...By saying that the guppies are still ok, you are seeing if you can get away with it. Don't get you...or I missunderstood ;) You really should test the rock before it potentially messes with your tank chemistry.

Fizzing rocks with acid is an indicator of a carbonate type rock. This rock will dump carbonates into your water (KH will shoot up). If you are doing a planted tank, this is not what you want. Certain fish also won't appreciate it. Not sure about guppies though.
No, I was testing it with the feeder guppies. I had never heard of testing with vinegar before. It is in a five gallon tank with 3 feeders from my crayfish tank. I thought that would a good way to test it if it was safe. I've tested driftwood that way before if I really didn't know what kind of wood it was. I've lost a fish yet. I guess I should find out what the KH of my tanks, our tap(well water) and the test tank is at and test everyday to see what the change is.
When you test it with vinegar and it fizzes, does it fizz like crazy or to you have to stare at it forever to see if it fizzes a few bubbles at a time?
Does the rock(s) fail any of Roger Miller's five tests "to see if a rock might wreak havoc with your water supply or do something else rude, crude or aquatically unacceptable"?
muriatic acid

Yes, I think Roger is right in using 10% hydrochloric acid (muriatic acid). This is commonly used to etch concrete and probably available at Home Depot. I think I've heard before that vinegar is not strong enough to really provide a reliable test.

Steve Pituch
Well the only one that it doesn't pass is the fizzing one(I haven't done it). So hydrochloric acid 10%, well, maybe I try the vinegar first and if I have any doubt find some hydrochloric acid.
I think it is a sedimentary rock of some sort because it has an imprint of a leaf on it. Anyone know what rocks usually have fossils in them and if they are safe?
I may just have to wait for spring and go collecting in the mountains near us for different rocks and more driftwood. I'll see if I can find slate or granite because I know those are safe.
You could post a picture of the rock, and we could give a guess as to what it is.

Well, I've been looking at the rock closer and I think its maybe sandstone or something like that. I took some pictures of it with my cheapy digital camera, it was still damp, its got some reddish spots that aren't real visible, but it is mainly grey.


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Well, I tested it with vinegar in several spots and ONE spot fizzed. So I guess it is not aquarium friendly. I'll have to find another rock I guess. :(
That was a great link cS, T'anks for posting that.

"When you test it with vinegar and it fizzes, does it fizz like crazy or to you have to stare at it forever to see if it fizzes a few bubbles at a time?"

I've had one rock fizz on me using vineger, it didn't fizz all that much but it was enough that I didn't want to risk it in the tank.

As for testing in a stocked tank. As far as I'm aware (feel free to correct me where I'm wrong :wink:) rock, and wood aren't likely to outright kill your fish the moment you put it in. Rather they will alter the water quality enough to cause some stress. Some exceptions to this might be any fungus or bacteria that might come in on untreated decor, or a sharp rock that could cut.

If rock or driftwood were to alter kh and/or ph it isn't likely to happen the day you put it in, it may take 2-3 or even longer depending on size of tank size of addition ect.


able_ranui said:
Well, I tested it with vinegar in several spots and ONE spot fizzed. So I guess it is not aquarium friendly. I'll have to find another rock I guess. :(
It's not the end of the world. If you have some sort of star-crossed attachment to the rock :biggrin:, then simply soak it in a Muriatic acid solution (1 part acid to 1 part water) until the fizzing stops. Then, it would be fine for aquarium use.

Muriatic acid can be found in any hardware/home improvement stores (in the paint department) very cheaply.
I scratched the rock and then checked it, would that make a difference in the soaking in acid results?

I am unsure as to what you are asking, but the soak I mentioned is meant to dissolve away those parts of the rock (carbonate-based portions) that would alter the tank's water chemistry. When you scratch the rock, you are increasing the surface area for the acid to react so that you would be better able to see the "fizzing" action, if any. When you do observe the fizzing, then the rock will alter the KH (and other parameters depending on the composition of the rock); and thus, should be discarded. However, if you are VERY attached to the rock, then a soak in a strong acid solution (like Muriatic acid, which is HCl) would hopefully remove the "bad" portion of the rock. I suggested that you should dilute the muriatic acid with water because the MA that the store sells has very pungent and dangerous fumes that aren't very good for you if inhaled. :D

Please let me know if I am misunderstanding your question.
Yes, you understood my question. Thanks for the clarification.
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