# Are these rocks safe for fish tank?



## theboothsociety (Jan 3, 2012)

Are these rocks safe for fish tank? Anyone know what type they are? Me and my gf went on a mission and stole them from this new mall that is going up near me. They have thousands of these rocks lining all of the roads in the mall.

Any tests or precautions to take, besides obviously soaking and cleaning them?


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## 13razorbackfan (Sep 28, 2011)

They look fine. There are VERY few exceptions to rocks for your tank. Might be limestone.


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## lilcountrygal (Dec 27, 2011)

13razorbackfan said:


> They look fine. There are VERY few exceptions to rocks for your tank. Might be limestone.


+1 .... Limestone. They look exactly like the ones I have in my tank. They look awesome in the water too.... the white lines in the rock really pop with black substrate


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## theboothsociety (Jan 3, 2012)

These rocks have little shiny specks in them, it's hard to see in the pics. I don't know I'd it's limestone, but if it helps the street they were found on had rock walls on both side, the probably used the rock from te ground when they blew out the road.


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## Jarrods (Sep 11, 2011)

Looks like granite to me.


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## PfunMo (Jul 30, 2009)

When I think of rocks and safety, it is not the type of rock which concerns me as much as the history of the rock. The rock is safe but what is on/in the rock is another question to me. The closer to people, the more likely the rock is polluted with something. That doesn't mean they should be thrown out but just treated with more care. Along a driveway at a mall is a good place to find weed killers, road oil, and gasoline. These are things that can stick on and not show very well so I would treat them just to be sure. Bleach is a very safe way to remove oily stuff. That's why it is used to clean shirt collars. Put them in water with 1/2 cup or so of regular bleach (unscented is prefered) overnight, rinse them off and lay them out to dry. That will remove any oils, etc. which will just float around and land again if you try to boil them. At the same time, you will have killed anything like algea, bug eggs, or fungus that might be hiding on them. 
Your big danger is splashing the bleach on your clothes! Not good.


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## theyangman (Nov 5, 2011)

Do the vinegar test.

place some drops of vinegar on the rocks, and if it sizzles, or reacts in anyway, then it's not a good idea to use em in your tank.

If there is no reaction, then toss em in a water bleach mixture for a day and then give them a solid rinse, air dry (any remaining traces of bleach will evaporate) and then they are good for the tank.


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## Mike_G (Nov 8, 2011)

Jarrods said:


> Looks like granite to me.


+1


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## Woodworm (Jan 3, 2009)

theyangman said:


> Do the vinegar test.
> 
> place some drops of vinegar on the rocks, and if it sizzles, or reacts in anyway, then it's not a good idea to use em in your tank.
> 
> If there is no reaction, then toss em in a water bleach mixture for a day and then give them a solid rinse, air dry (any remaining traces of bleach will evaporate) and then they are good for the tank.


I disagree with that statement it is an old fish tail. Read this ( http://www.cichlid-forum.com/articles/rock_metals.php ) and it will answer most of your basic questions on which rocks are safe


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## Fishy_Cichlid (Aug 4, 2011)

IMO those rock look like Basalt.

http://www.es.ucl.ac.uk/schools/Glossary/basalt.htm
http://itc.gsw.edu/faculty/tweiland/igrx.htm

If Basalt, they can surely be used. I use them in my tank. Totally non-reactive and very safe. We call them mountain rocks and is used for construction & road.


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## Fishy_Cichlid (Aug 4, 2011)

Check out here -
http://www.cichlid-forum.com/phpBB/view ... 7ad3f56b55
http://watershed3.tripod.com/rocks.html
http://www.bcaquaria.com/forum/freshwat ... idea-3455/
http://www.cichlid-forum.com/phpBB/view ... be278a7077


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## Fatal (Jan 15, 2012)

They are some BIG rocks haha. But yeah they look fine, they're smooth for starters.


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## theyangman (Nov 5, 2011)

Woodworm said:


> theyangman said:
> 
> 
> > Do the vinegar test.
> ...


*shrug* good read, perhaps I was overly cautious? Beats me. I simply purchased rock ahead of time from a reputable source instead of stealing them from a mall parking lot, so I never had these concerns.


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## PfunMo (Jul 30, 2009)

The vinegar test is based on a faulty idea for the current group of fish that many favor. It's also based on areas that have soft water. If you put acid like vinegar on an alkaline rock like limestone, it may fizz or bubble. That doesn't mean the rock is bad! It means that it may tend to change the PH/KH if you have soft acidic water. Whether that is a good thing or not depends on what fish you want and if you want to change the water. 
Just another one of those myths written by somebody way back and passed around ever since.


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## Bahilman (Dec 24, 2011)

Mike_G said:


> Jarrods said:
> 
> 
> > Looks like granite to me.
> ...


+2


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## PfunMo (Jul 30, 2009)

Since I don't hear of much limestone in your part of the world and with the shiny bits showing, I would expect broken granite or marble would be the more likely choice for cheap decor along driveways. The little shiny bits might be quartz embedded. Not likely to do any harm, either way, though.


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## theboothsociety (Jan 3, 2012)

Great. Thanks for the feedback. I scrubbed them good today and they are now soaking outside in a tub of water with a cup of bleach overnight. I think they are granite with possible quartz inside like PfunMo said above. They dont look like any of the other rocks suggested. They also look totally different when in water, they are a dark grey/black with light grey and white, with shiny specks.

My next question: I got this huge rock (below) which has gotta weigh close to 50 lbs or maybe more. Its gonna be tough to even get up over the tank to put it in. I tried to take a pic with my foot in there (size 9.5 haha) for size comparison. Is this rock too big or weigh too much for a 75 gallon?

I also noticed when scrubbing a few rocks have a tiny bit of rust on them. Should this be a concern?


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## PfunMo (Jul 30, 2009)

For me, it would be too much. Depends on your outlook, some. I don't like to mess with the hard stuff! I go for stacks of smaller rock as I find need to move them often. I also find less hazard in moving smaller rocks than the big heavy stuff that gets slick when wet. I cring at the thought of dropping one through the glass side or bottom. The small amount of rust one normally finds in rock is not a problem. If you think of how long it takes for rock to decay enough to release much of it even if it were pure iron ore and compare that to the amount of water most of us change, there is little chance of any real buildup. Tanks go for years with metal screws and bolts dropped in them without harm. If metal were a real hazard to fish, I should think we would see tighter lids on shop tanks.


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## leftieaz (Jan 29, 2012)

Those are huge rocks. It'll just displace too much water. What you really want is rocks of various sizes to build caves and hiding places. You can possibly try smashing up the rock with a large hammer.


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## theboothsociety (Jan 3, 2012)

I decided not to go with the one huge rock. I was gonna do it until I got the chair ready and lifted the rock over the tank and I was like NOPE. It'll just be too much of a pain when it comes to maintenance. Im glad I decided against it because even the other smaller rocks are big in that tank.

Im now on the hunt for some new smaller ones...

Heres a video of them in the tank. With a few other randoms still.


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## 13razorbackfan (Sep 28, 2011)

theboothsociety said:


> I decided not to go with the one huge rock. I was gonna do it until I got the chair ready and lifted the rock over the tank and I was like NOPE. It'll just be too much of a pain when it comes to maintenance. Im glad I decided against it because even the other smaller rocks are big in that tank.
> 
> Im now on the hunt for some new smaller ones...
> 
> Heres a video of them in the tank. With a few other randoms still.


Why not just break it into pieces?


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## theboothsociety (Jan 3, 2012)

I tried to smash it on the ground but it wouldnt break. I probably would've if I had a sledge hammer handy but then I have to worry about pieces flying everywhere. The place where I get them from is only 5 mins away and are readily available. Probably more effort to break than finding new ones.


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## ph1sh3r (Jan 20, 2012)

That is Gneiss. Gneiss is a metamorphic rock, it used to be granite, then millions (probably billions in your area ) of years of pressure and heat metamorphosed the granite into gneiss. There used to be a massive mountain rage (grenville) that crossed that area about 2.8 billion years ago.

should be safe for the fish, i would watch out for rusty spots or any black/grey quartz, quartz turns dark after exposure to naturally occurring radioactivity (actually very common)


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## prov356 (Sep 20, 2006)

Rust on rocks does not harm fish. Few rocks aren't fish safe. Very few. Pyrite (fool's gold) is one. See Suitability of Rocks in the forum library.


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## theboothsociety (Jan 3, 2012)

Yup looks a lot like Gneiss. Some of them look totally different. Good to know.

I just recently got a new batch of smaller rocks, and after soaked in bleach/water solution and a good srub I had them out drying in the sun and noticed about half of them had rust spots.

Im probably not going to use some of the really bad ones, because they are just ugly but are you sure rust is OK prov?

Here is a pic of them in the tank.


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## fmueller (Jan 11, 2004)

I hope you don't mind me playing around with the image in GIMP! Your aquascape looks great - good sized caves, but still a very natural look :thumb:

Just to give you a second opinion on the rust, I agree with Tim. A bit of rust in a tank doesn't harm the fish. Case in point, I weigh my driftwood down with stones that I attach to it using 3" drywall screws. After a few years, the screws have usually rusted away for the most part, separating the wood from the stone. By that time the wood stays down by itself. But anyhow, the rust from the screws has never caused my fish any problems.


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## theboothsociety (Jan 3, 2012)

Thanks I am glad you like it. I definitely do not mind at all. Look at the image I uploaded to my tanks section last night. I messed with it in photoshop. Our images look almost identical. :thumb:


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## flybywags (Feb 17, 2012)

It also looks a lot like Carder Rock from Maryland.


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## theboothsociety (Jan 3, 2012)

*** come to the conclusion that there are multiple types of rock in these rocks. LOL.

They all look very similar but are slightly different. Some have shiny speckles, some don't. Some dark almost black, some grey and some white-ish. Others have pieces of this quartz looking rock seen below.

Check out this one I found in my bucket full of rocks. Anyone know what this is?

Almost looks like something I can break into pieces, tie it to a rope, call it costume jewelry and sell it way over priced.


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## MalawiBlue (Dec 11, 2002)

This one is quartz.


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