Is this rock safe to use? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 8 Old 09-18-2011, 10:47 PM Thread Starter
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Is this rock safe to use?

Hello, it has been a long time since I have been here but I have decided to make over my tank a bit and have a question. I hope the attached pictures are viewable, I have never used pictures in a post before.

I bought some "casco tufa rock" from my LFS. I plan to use it to attach java ferns. I chose these rocks because they were a good size and seemed to be rough enough for the ferns to attach. My question is if this is safe to use in my aquarium or should I do anything to them to make them safe?

There are small round yellow and blue growths on the rocks. They do not come off easily. They could be some kind of mold-like organism or some weird crystal. I really have no idea. I left the rocks sit in a bucket of water for a week to see if it affected the water parameters at all. The ph is the same as my tap but the ammonia, nitrite, and nitrate levels were all above 0. That seems odd to me since it was just the rocks by themselves. Is it normal for rocks to raise these levels and should I be concerned?

If it is helpful information, I have a 5 gallon hex with 1 beta. It is planted but only the java fern does very well. It has been running for about two years and is cycled. I greatly appreciate any insights you may have as I am a bit of an amatuer.




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post #2 of 8 Old 09-18-2011, 11:24 PM
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Hi, Welcome back to TFK.
I'm not an expert but there are a couple of things you can do. Pour vinegar over them to see if they fizz. If they DO, they are NOT safe for the aquarium/fish. If they do not, then they are ok. I also read somewhere if you have the product "PH down" it will also work. It is an acid based product too like vinegar.
Also if you have the correct testing kits, you can test your tank water's hardness, I think GH and KH, and after the rocks have been in there a few days to a week, check again for any changes. Hope this helps.

Every kid, regardless of what they are going through, is ONE caring adult away from being a success story. ~ Josh Shipp, Teen Behavior Expert
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post #3 of 8 Old 09-19-2011, 12:11 AM
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If you are worried about growths on the rocks you can pour boiling water over them several times, or actually boil them though some will say this is not safe. I've done it several times and no problems. Or you can soak them in a bleach solution, rinse them well, then soak in water with a good dose of water conditioner.
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post #4 of 8 Old 09-19-2011, 12:27 AM
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Most rocks can be used in a tank but it depends on how well you clean em.
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post #5 of 8 Old 09-19-2011, 08:07 AM
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I have always used rocks i gather outside, as long as they are not soft (crumble easily), have harsh minerals (limestone, iron, calcium buildup ect.) and are free of moss. I have never had a problem, i wash them off and let them soak as someone else suggested, and have had some great looking decor. I do not see the point of buying rocks, when you have them right at your feet! (unless it is live rock for a saltwater tank, I am pretty sure it is illegal in most places to harvest that on your own!)
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post #6 of 8 Old 09-19-2011, 10:26 AM
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The vinegar/acid test only works to determine if the rock is or is not calcareous. Calcareous means composed (made) of a calcium type mineral such as limestone, dolomite, marble, lavarock. The "fizzing" if it occurs means some such mineral is in the rock, and this will dissolve slowly into the water, raising hardness and corresponding pH. So this test tells you nothing else about the rock. This calcareous rock is fine in livebearer tanks or rift lake cichlids, but should not be used in tanks with soft water fish.

Rock is porous depending upon the type, and thus absorbs liquids. If it was exposed to oil, gasoline, fertilizers, pesticides, etc., these may be in the rock. I am not sure that any amount of washing can remove these substances. And along the same lines, I would not recommend using bleach to clean rock, as this will also be absorbed. Same with salt water. The amount released over time may be minimal, but still doesn't belong inside a fish tank.

A good scrub with a stiff brush under hot water is all I use on rock. I have used lace rock purchased from a fish store, and I have used basalt slab rock and rounded river rock from a landscape supply. I recognize there is a risk to any rock (or wood for that matter). "Soft" rock that crumbles should never be used, only rock that is hard.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #7 of 8 Old 09-19-2011, 10:29 AM
if the rock is in fact tufa, it is calcareous. (google tufa). it probably isn't a good idea, since you have no idea what other minerals it can contain.
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post #8 of 8 Old 09-19-2011, 10:53 AM
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Thank You Byron for explain the "Fizz" test!! See I learn something in here every day!!

Every kid, regardless of what they are going through, is ONE caring adult away from being a success story. ~ Josh Shipp, Teen Behavior Expert
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