# Judging Rocks For Aquarium Use



## Teebo (Jul 15, 2015)

I have picked some rocks, and boiled them for several hours with salt and a little bleach. Then read about the scratch and acid tests, I am yet to locate some acid to use but I have put them in two piles based on appearance, safe and potentially not safe. 

These rocks seem solid, consistent color and the internal grain where they have been broken proves this. I would assume these are completely safe.


















These on the other hand I am leary about. I suspect they contain metals due to their orange-maroon coloration. The large one on the bottom appears solid until you see a metallic vain running along one side, and at least one of them smells like sulfur. What do you think?


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## FuelingFire (Nov 8, 2012)

Someone may chime in a little more knowledgeable But you can use white vinegar to test the rocks, and if it fizzes it just means it will affect your pH. the ones with the Metals are a defiantly No.. I had found rocks that had Iron pyrite in them as well as some rust and was told they would affect my tank and be harmful to the fish. as far as your first set of rocks they seem fine. also something I learned in this hobby is you don't need to bleach everything to put into the tank. As I have figured anything that lives out of water can't live under water, and anything underwater can't live out of water. if you give some time to either affect. Bleach to me is a very dangerous thing to be using for anything in an aquarium. their are better ways to clean decor. also boiling is fine to do as well with out bleach. it just my opinion. but someone more knowledgeable on rocks maybe able to help you.


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## Teebo (Jul 15, 2015)

Thanks, the vinegar has a very weak percentage of acid and you need a magnifying glass to observe the reaction which is why most people do not use it from my research. Bleach from what I have learned begins evaporating from the water the instant you add it, so there is never any harm of it getting into your aquarium system as it dissipates very quickly. Helps remove tannins from wood very quickly I noticed. 

I will avoid reddish-orange rocks due to iron from here on out.


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## FuelingFire (Nov 8, 2012)

Your welcome, But I would be very cautious about bleaching wood, I was told by someone on this site who I respect a great deal who no longer is active, Name of Byron that Bleach can linger in wood for years and even if the vapors disperse from the water. the actual Chemical compounds do not. And that can be just as dangerous. I mean if you think about it when Bleach stains your cloths the compounds are left in the fabric. only the vapors disperse. Just one last example we use prime and other bonding agents to bond chlorine and chloramines compounds from our tap. it doesn't mean the chemical is actually out of the tank. its just less harmful. when you air out your tap water yes you make it safe to use but most of the compounds are still present. Of course I am no chemist and am only giving my opinion. But Byron taught me not to use it on wood due to the porous nature of wood and how it can trap in the wood for years. But again My opinion and I mean no offense if I seem pushy I Just Don't trust bleach.


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## natemcnutty (May 26, 2016)

Carbonate reactions (fizzing) are unreliable which is why many don't use it. Anything with trace amounts of calcite will fizz even if it would be safe enough for a tank. Having no fizzing still doesn't mean that it is safe, but the acid test is really only useful if you know how to gauge the vigor. Here's a good explanation: http://geology.com/minerals/acid-test.shtml

Next time you do a water change, leave a bucket of water to sit a few days, test the ph and gh (and maybe tds), then put one of the rocks in, wait a week or two, and then test it again. This will give a general idea of what it will do in your tank. 

As for the bleach conversation, I wouldn't soak driftwood or really porous rock, but a bleach dip with a good rinse or soak afterwards should be fine. 

Sent from my Nexus 6 using Tapatalk


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## PlantedRich (Jul 21, 2010)

The idea that bleach can linger in wood neads a bit of thought?

Simple bleach of the type we use, without color or scents, is made of three things, water, a form of salt, and chlorine. Can we accept that water and salt are okay but the chlorine is the thing we worry about? 

So what can we find about chlorine? It is normally a gas and we have to do some tricks like tie it to salt to keep in the water longer so we can store it for a while. We also can read on chlorine and find it reacts very readily with organics. Organics in this use means carbon bearing compounds. Not organic gardening! 
So can we agree that wood is an organic? So can chlorine that reacts with organics like wood stay in wood without reacting? Once chlorine comes into contact with wood, there is a chemical reaction until one or the other is depleted. 
In most cases the chlorine is used up and gone before the wood. In the cases where we splash bleach on our shirt, it is often the shirt that breaks down first! 
Unless somebody can show me a chemical reaction that can lie dormant for years and then suddenly come out when we add fish, I find chlorine is totally safe to use on tank stuff. 
Another good indication that it is safe is the number of experienced hobby folks who use it all the time. 
Unfortunately, there are those who have not used it and continue to spread what they have been told without thinking about it or trying it. 
Don't simply something like this that you find on a forum. Do some reading and decide. Reliable info is out there for the reading. Here are a couple sites to check:
First paragraph, first sentence? 
It's Elemental - The Element Chlorine

Less reliable being Wikipedia but still lots of info:
https://en.wikipedia.org/wiki/Chlorine


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## Teebo (Jul 15, 2015)

PlantedRich said:


> The idea that bleach can linger in wood neads a bit of thought?
> 
> Simple bleach of the type we use, without color or scents, is made of three things, water, a form of salt, and chlorine. Can we accept that water and salt are okay but the chlorine is the thing we worry about?
> 
> ...


I think you may have been the one who educated me on this back when I had my blueberry branch driftwood thread, using bleach there. From a pool-perspective I can not keep free-chlorine in my pool for longer than a week. In that sense concentrated chlorine that can fit in my hands, evaporated from a pool within a week. Boiling water with bleach in it I am sure speeds this process up dramatically.


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## FuelingFire (Nov 8, 2012)

@PlantedRich; I never claimed to be a chemist, And honestly I have used Bleach before on items for a tank. when i was still new in the hobby, I bleached driftwood and other decor. was talked out of it. I'm not ignorant to the fact, But like anything in this hobby their are two sides. and a lot of debate on the bleach. Personally I just looked at the ingredients of bleach, and the 2 types that are used in households. Yeah sure they are salts, but do you still want the salts in a tank. esp.. if you have fish that are sensitive to salts. But it doesn't matter Honestly I'm not as ignorant to fact as you make it sound. and I guess, I did shoot off my mouth, (keyboard) But I can tell you I never trusted bleach. Because your still taking something and making it a harmful chemical with natural compounds, than expecting it to break down. back to a natural state. from what i read about it the chemical still remains in the salts after break down. even after it is gassed off, It may be safe to use. But really why take that chance. I'll man up and say I normally go by what I am taught and what i research, But That's the Key you have to research. Yea I took someones word for it when i was younger. and I do it again if it means I keep a chemical out of my tank even if their is still a hint of a chance it can be introduced in my tank. Why do i want the risk. And I still am learning in this hobby. But that's whats great about this hobby. I'm like everyone else here I only want the best for my fish, and Everyone has their own methods.


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## someoldguy (Feb 26, 2014)

I'll go along with Rich . I've been using bleach as a general tank / equipment / substrate(gravel) disinfectant for decades . Haven't found anything that it won't kill off . Just pull the fish and plants , dump some in the tank , let the filter run for a day or 2 . Drain , rinse everything REAL well , and you're back in business . Though I'd let wood dry out for a few days in the sun , just to let anything that's soaked into the pores outgas .

Quick thought ... Don't think I'd use it on stuff like Aquasoil , simply because I don't know for sure what its' made of .


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## FuelingFire (Nov 8, 2012)

I do bleach dip my plants. But Only because I hate bladder snails. but than i QT my plants in a separate tank for a month. for 2 reasons. 1 to make sure the plants will survive. and also to make sure I never have any bladder snails.. But Never on any driftwood or rocks. I should add I haven't done it in a long time.


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## PlantedRich (Jul 21, 2010)

FuelingFire said:


> @PlantedRich; I never claimed to be a chemist, And honestly I have used Bleach before on items for a tank. when i was still new in the hobby, I bleached driftwood and other decor. was talked out of it. I'm not ignorant to the fact, But like anything in this hobby their are two sides. and a lot of debate on the bleach. Personally I just looked at the ingredients of bleach, and the 2 types that are used in households. Yeah sure they are salts, but do you still want the salts in a tank. esp.. if you have fish that are sensitive to salts. But it doesn't matter Honestly I'm not as ignorant to fact as you make it sound. and I guess, I did shoot off my mouth, (keyboard) But I can tell you I never trusted bleach. Because your still taking something and making it a harmful chemical with natural compounds, than expecting it to break down. back to a natural state. from what i read about it the chemical still remains in the salts after break down. even after it is gassed off, It may be safe to use. But really why take that chance. I'll man up and say I normally go by what I am taught and what i research, But That's the Key you have to research. Yea I took someones word for it when i was younger. and I do it again if it means I keep a chemical out of my tank even if their is still a hint of a chance it can be introduced in my tank. Why do i want the risk. And I still am learning in this hobby. But that's whats great about this hobby. I'm like everyone else here I only want the best for my fish, and Everyone has their own methods.


The part I resist is the idea that chlorine is a "chemical" and too many people seem to imply that they put no "chemicals" in their water. What is there that is NOT a chemical or a group of chemicals. Rather than just saying we don't want chemicals in our tanks we need to think about chemicals and what they or don't do for us. We might say chlorine is bad but then we find that one of the most common places to find chlorine is salt (sodium chloride) Yet we can also find that salt is often using alone or in medicines for fish. Even the water is hydrogen and oxygen! 
So rather than thinking blindly that a particular chemical is bad or good, I like to look at what it does or doesn't do that I want or don't want. 
Take the hydrogen out of water? Not going to be good for the fish. 
Take the O2 out of the air we breathe? 
Take the chlorine out of the water we drink and it gets too nasty to drink. 
So the point gets back to what we actually know about each chemical and how it is used. All of them are dangerous If used in the wrong place, amount, or time. 
Time and experience has shown many people that bleach is a really good thing to sterile stuff. It isn't like it is some foreign item that is unusual and we should avoid it. It is the most commonly used thing to treat the water we drink or add to the tank. Avoiding chorine is not possible and we live with it. Lick the back of your hand and you will probably taste sodium chloride, so keeping chlorine out of a tank is just not going to work! 
Millions of people world wide use it daily and find it is a good tool when you want something sterile.
I have a tub full of wood soaking in bleach water right now! All my rocks and wood have got the same treatment for many, many years.


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## FuelingFire (Nov 8, 2012)

haha Drink bleach right out of the bottle and see how that affects you.. Lol no seriously don't do that. But I get what your saying. And yea we do need it for a lot of things. But I think I will go back and research Bleach and the home aquarium again. It has been years since I last researched it. and I'll man up and look at it again. Whether it changes my opinion. we'll see, If it does I'll let ya know. I won't hijack the Op thread any longer. I been wrong before And probably will again. But thanks for the school.


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## PlantedRich (Jul 21, 2010)

Rocks are one of the good / bad things to clean with bleach. It gets them sterile so it does make many safe to use but then we often look for rocks based on appearance and soaking them in bleach water can change the appearance. Texas holey rocks are often sold for a higher price when they are a pretty white color. But that color can be changed when we take a rock that has lots of dark lichen on the surface and bleach it white. Take some very expensive rocks and soak them in strong enough bleach and you may not like what you have left. 
So for the OP question of what is a safe rock or not, there is often a two part question. We can sterilize it and it is safe from that standpoint but still the effect it may have on our water is still there. Gets back to the chemical question again. Testing rocks or any other dealing is often a question of relative strength of the chemicals involved. Take a really alkaline rock like limestone and a weak acid may make it bubble or fizz. But a less alkaline rock will still bubble and fizz if you use a strong enough acid. It takes some judgement and knowing what strength of acid makes what amount of reaction. So it can be a handy test if you are used to doing it and know what amount of reaction to get before ruling the rocks safe/ unsafe. 

Rather than suggesting a test of this sort to the person who has not used it before, I like to go with a test more specific to what the person may find in his water. Water can be anything from acidic to alkaline so if you want to know how it works out in your water, I suggest testing for change in that water. It doesn't really matter too much if it bubbles in acid if your water is always going to be alkaline, does it? But it does then involve the amount of buffering your water has. Little to no buffer and your rocks may make a major change. But if you have very hard alkaline water and throw an alkaline rock in, you may not be able to measure any change. 

When faced with doubts of this sort, I go with letting the rock soak in the water I will use in the tank and then seeing what the result might be. Otherwise it is just going to be somewhere near a guess. For my personal use, I just go with making the rocks sterile and then wait and watch the tank water. It is not going to be a dramatic overnight situation in most cases but a slow creeping complication that you may/ may not need to change.


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## Teebo (Jul 15, 2015)

Okay so clearly the better choice would be testing a bucket of water with the rocks in it. I will try this. In the meantime I have further suspicions that the test will likely not proove. 

I have been sticking with these "blueish" rocks almost the color of faded pavement, since they have a solid consistent makeup. I am not worried about rust with these rocks, however there is some surface oxidation which I am suspicious came from other rocks in the bunch where they were dropped and it just stained the surface. On the other hand I see a teal colored patina that usually comes from copper....I think I would rather have traces of iron in my water than copper so now this is really concerning me.


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## PlantedRich (Jul 21, 2010)

Maybe good rocks, maybe not? We get to do a lot of things that take a bit of guessing how it will turn out but thinking first is really a good step. 
So what is the big thing to worry about? Do you plan on fish of animals that tend to be famous for sensitive? That takes a far different approach. But what I find is that rocks are out and about in the weather for a very long time and as such , they degrade very slowly in most tanks. What is your water like? Soft, alkaline water with little to no buffering makes things like choosing rocks and wood much harder. Things drift much quicker if the buffering is low. 
I have almost always wound up in areas with hard alkaline water when keeping fish and that has made it easy to choose. Does your water tend to be like acid so that the rocks degrade quickly or is it less difficult so that frequent water changes takes care of any drift? 
I think of rocks, rust and all the other pollutants as just another item to keep under control. If I have rocks with copper, I never see it due to buffering and water changes. Perhaps some study on the "what-ifs" might help? Cheap or expensive animals? What is the main driver of the worry? 
Just for info, most common rocks are not rich enough in ore to make them valuable and the odds are good that your rocks are not poison as such even though they may tend to make the water parameters drift.


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## Teebo (Jul 15, 2015)

I am using these for a shrimp tank, they are very sensitive to metals. My water I believe is on the harder side, and whenever I test my alkalinity it reads almost none (from what I gather this is my buffer, the alkalinity).

My water changes are at minimal, I try to walsted them for the most part. They are spotless and nitrates are insanely low, water change is about 20% once a month or so. I like to make a practice of bi-weekly 10% but that does not always happen. 

It is good to know that I would see my buffer (drop?) if the rocks had an issue/contaminant! I am still learning, you never finish learning in this hobby.


This is what I have come up with for a hardscape using these rocks, once they are elevated it will appear they caused the roots to grow around them.


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## PlantedRich (Jul 21, 2010)

I like the thoughton the layout. I do a fair amount of prowling around rivers and it does often get things arranged that way. Either the roots grow around the rocks or the two get tangled together during floods, etc. Either way, I see it often. 
Now to what is safe? I see the reason for more concern than some about rocks, etc. 
With the water, low water change and sensitive animals, it pays to be more careful. I'm more fish guy and no shrimp at all but this would be my way for my fish. When in doubt, I try it carefully at first to see how it goes with some that are less valuable. Breeding fish almost always winds up with some which are not going to grow to be useful or that we would want to spawn so I do have to cull some. Those are as good as any to try out new, somewhat risky tanks. 
Any way to see a plan to try a couple for a month or so? 

Meanwhile on the rock color, it may not be what it looks like at first. Red reminds us of rust because we see rust. But lots of other chemical things go on in the ground to make the same red color. There is a locally semi-famous river called the Red River separating Oklahoma and Texas. It is truly a red color and the color has nothing to do with iron ore. Color alone is not a good ID on things. Georgia red clay stains the rocks but is tank safe. 
Bottom line may be that the rocks are fine but then it pays to be prudent !!


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## Teebo (Jul 15, 2015)

Unfortunately I am limited on time, I am preparing this for a tank I am building ay my girlfriends. I live 8 hours away so this is all going on a plane with me, and I won't be back for several weeks so all I can do it set it up and let it cycle with the rocks for a month. Check it when I return. 

Red is imo the most desirable opposite of the color spectrum our plants are, great contrast. I come across red with red spots all the time I refer to as "blood rocks" they are not metals it is something else, often they are marbled with white and red. I would love to use some of these "blood rocks"


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## PlantedRich (Jul 21, 2010)

WOW! That is one bloody looking rock! 
I've been reading a nice book on roadside geology that is giving me lots of new info on how rocks are formed and why we find so many different types. The more I read, the less worried I am about finding the rock that will kill my fish. There are so many rocks and so few that are dangerous that I'm feeling more bold! 
In your case, you do have some major problems with the remote setting. Assume there is no water on hand that will be in the tank in the long run? No practical way to get the rocks and the future water together for a test before the trek? 

With all these restrictions, I go with the idea that it is likely to work fine. But then I also tell the girlfriend that it may have to be changed. Don't want to make promise far more than you can deliver. Nature has a way of showing us who is in charge!


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## PlantedRich (Jul 21, 2010)

Meanwhile are there any geology trained folks here that can tell us how this rock got the really red color. I've been reading about how the Red River gets it's color but I've not seen any this bright even when wet. I might guess it is a rock that was lifted into the ground water to make the cracks and then the color moved in from a layer above? Anybody got good info on what works to make such vibrant color?


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## sfshrimp (May 24, 2016)

*thought*

Put in a bucket with a airstone, test the water. See what happens. Is GH or KH up? Is it inert? I had some seriyu stone I bought for a small five gallon and it screwed my water, as pretty as they were. What you have is red veined quartz.

Bump: also...

http://www.plantedtank.net/forums/120-aquascaping/96268-quartz.html




sfshrimp said:


> Put in a bucket with a airstone, test the water. See what happens. Is GH or KH up? Is it inert? I had some seriyu stone I bought for a small five gallon and it screwed my water, as pretty as they were. What you have is red veined quartz.


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## Teebo (Jul 15, 2015)

*I bought some "Ohko Dragon Stone" off eBay, does anyone know if this stuff is generally inert or not? It kind of appears metallic to me, a rusty color.*


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## sadchevy (Jun 15, 2013)

The only thoughts I have on this are...1- all the animals we keep started in the wild ..2- the water they live in ran over or through all kinds of rocks and soils to get where it pooled...3- the animals adapted to the conditions of the water. I understand the fear of introducing something that may in high enough concentrations be harmful to the animals. But in reality, it takes years if not eons for most rocks to dissolve in water. I'm with PlantedRich on this, you are more likely to find safe to use rocks than not. I use limestone, sandstone, or just about any form of rock I find around my property and have never seen a change in my water parameters that has made me worry. It may be I have a good neutral water supply or it may be that it just takes to long for the rocks to affect my water in a way that worries me. You have concerns about putting metals in the tank because of shrimp, you do realize the water you are using is stored in local lakes, metal storage towers, flows through iron and copper pipes, has multiple chemicals added to purify, all before it ever gets to our house faucets. Once there it may flow through, depending on the age of the house, iron, copper, pvc, brass. All these things have very little to no impact on the water because they are in a very concentrated form(pure to a point). Now if you have acidic water(low to very low ph) you may see some affects from the rocks, but it will be a slow process, small changes over weeks or months. I have never seen rocks change things so drastically in a short period of time(meaning days) that it killed animals. We have to step back and remember that these glass boxes we keep fish in are no where near natural. We as hobbyists do our best to give proper care and living conditions to the animals. There is no right or wrong answer. With water changes done at reasonable intervals, there should be no problems with the rocks you choose.


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## PlantedRich (Jul 21, 2010)

While we are trained to think of that rusty color as being iron, it is not very likely to be. Think of the wonderful find of you could find iron ore in that large amount and concentration! There are lots of other ways to get the brown we call rusty. It is not possible to say from pictures but I might think those are a sedimentary rock that has then also been reheated, melted and reformed. When they scratch them do they come off in small grains like sand? My po' boy name would be sandstone! 
The Ohko Dragon Stone name may simply be to make it sell better more than anything else.


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## Teebo (Jul 15, 2015)

PlantedRich said:


> While we are trained to think of that rusty color as being iron, it is not very likely to be. Think of the wonderful find of you could find iron ore in that large amount and concentration! There are lots of other ways to get the brown we call rusty. It is not possible to say from pictures but I might think those are a sedimentary rock that has then also been reheated, melted and reformed. When they scratch them do they come off in small grains like sand? My po' boy name would be sandstone!
> The Ohko Dragon Stone name may simply be to make it sell better more than anything else.


Yes it crumbles into sand easily judged on how it arrived, they are soaking in water right now so I tried rubbing them together and they turned into a mud/clay on my fingers. After rinsing them and soaking overnight they left a sand texture on the bottom of the tub.


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## PlantedRich (Jul 21, 2010)

Okay, that sounds like what many do just call sandstone and sand is almost always okay. The color can come from lots of places. The sand itself may have come from brown rocks or something that got mixed in as the old world was melting and churning them around. When we think about iron, it is not really easy to find in large concentrations and there are not too many around the country so finding rocks with really high levels is not too common while there are lots and lots of brown rocks and lots of brown sandstone. 

If interested in a short easy read on rocks, this is a book that tells it in a way I can read and pick out the points I want at the time without even attempting to remember it all! 
Great book for the kind of interest I have in the subject. 
A penny plus shipping is my level!
https://www.amazon.com/gp/offer-listing/0816016976/ref=dp_olp_all_mbc?ie=UTF8&condition=all


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## Teebo (Jul 15, 2015)

I have to say this stone kind of concerns me that it will "melt away" over time in my tank. No matter how much you wash the stone in the sink it continues to crumble. I get the impression it will erode and fall apart, as well as change my water since it is SO soft of a material  it honestly reminds me of clay and chalk mixed together....


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## PlantedRich (Jul 21, 2010)

Yes, that can happen. There are hard rocks and soft rocks and some that never really made it too far toward the rock stage so that they can be more "dirtrock" than sandstone? It can depend on what was being squeezed to make the rock and how much pressure for how long so there is really no way to say for sure. But I would go for a trial period and see how it works. The small bits of sand that might drop off would not deter me if I liked the rocks. 
This form of gardening has much in common with doing it outside in that there are very few sure things. Some years the same plants in the same spots work very well and other years they are a total failure. 
At least the rocks move slow enough that I have time to deal with them!!


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## Teebo (Jul 15, 2015)

I let the dragon/sand stone I wanted dry out, then I went to add it to my tank and as soon as it touched the water it started melting again. I really do hope if it stays submerged it will not continue to crumble at the rate I just witnessed. My tank turned into a snowglobe!


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## Bananableps (Nov 6, 2013)

I'm surprised no one has mentioned the risk of heavy metal contamination. Any time you spot what could potentially be an ore in a rock, there is a fair chance of that ore containing some nasty heavy metals that could cause serious developmental problems for fish. Rust is hardly ever _just_ iron.


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## PlantedRich (Jul 21, 2010)

Quote: 
Rust is hardly ever just iron.
A quick check of the definition of rust is needed? By definition, rust is iron corrosion--ferrous oxide. 

If one did have worries about some of the metals we might call heavy metals, we could use a product like Prime to take care of the problem. 
Not a big worry for most of us. Lead, cadmium and copper are some that I see most but they don't produce rust. What we often call rust colored is more often just the color and not a true iron ore.


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## Teebo (Jul 15, 2015)

Prime only binds the metals together, they are still present. I add a few drops of Prime to my tank on WC day to ensure the bonds have not broken down in the remaining water. 

Any input on my crumbling rock? The continuance of the crumbling once permanently submerged? I will never buy this rock again!


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## Bananableps (Nov 6, 2013)

PlantedRich said:


> Quote:
> Rust is hardly ever just iron.
> A quick check of the definition of rust is needed? By definition, rust is iron corrosion--ferrous oxide.
> 
> ...


Ores are never pure in nature. Iron ore can have heavy metals mixed in with it. You will find advice against choosing rocks with rust on them in any book on aquarium keeping.


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## PlantedRich (Jul 21, 2010)

Teebo said:


> Prime only binds the metals together, they are still present. I add a few drops of Prime to my tank on WC day to ensure the bonds have not broken down in the remaining water.
> 
> Any input on my crumbling rock? The continuance of the crumbling once permanently submerged? I will never buy this rock again!


At this point, I might guess that it will not be a good rock to keep long term. If it is crumbling now, I would see no reason for it to do less as the water fully soaks into the deeper and deeper spots. 
On the metals question, we are all likely to have several types of metals in the tank and at different levels as metals are a natural item in the landscape. We all use water that comes to us in metal of various types and is stored in metal water tanks. We know the metal is there and we deal with it easily. I have no idea if the amount of water we change or the way we treat our water for heavy metals is the cure. I do know a lot of people who kill their fish and I've killed lots of them. I do read lots of warnings about metals but as a hazard, I place it so low on the scale that it is not worth much time. 
Dirty water? Now that IS a real hazard!


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## MCHRKiller (Jul 25, 2008)

I use all sorts of rock I find out and about from sandstone to straight up limestone....IME they honestly dont bother the water that much. I have a 75G with a good 50lbs or so of Limestone and it has not really altered the water chemistry much. Most rock you find around waterways is fine to use in an aquarium. Naturally if you are keeping uber sensitive softwater shrimp....Id avoid rock altogether; however fish are very adaptive...even wilds. My personal concern would not be from the rock breaking down and raising pH, hardness, or containing small traces of metals...it would be from it being porous and absorbing random chemicals and pollution. Thus I soak mine for a few weeks and hope for the best.


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