# Are rocks that have rust aquarium safe?



## DaveK (Jul 10, 2010)

Maybe some rocks that have rust are aquarium safe, but I'd never trust them. After all, it's not too hard to find another type of rock that is safe to use. Why put your whole tank at risk over a questionable rock?


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## osmosis (Apr 19, 2017)

Rust? I'd be surprised if you have ferric oxide. It seems likely that you have a rust colored deposit on the surface. The classic thing to check for is carbonates, using vinegar or other acid and looking for bubbling. Other minerals can become soluble in acidic waters (CO2 injection or peet, or decomposition). These may not mess with the pH much, but can leach trace metals into your tank, for which most of us do not have color tests. The answer will depend entirely on what the deposit really is. Safe bet is to skip it.


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## PlantedRich (Jul 21, 2010)

As mentioned it is not really too common to find actual rust in rocks. One reason is that rust weathers pretty quick and as the rock has been out in nature for a few million years, it is likely to be gone. Far more common to find "rust colored" rocks which are actually other materials like reddish clay deposits. 
We often hear mention of rust as a hazard but then we often hear of Bigfoot, too. The metals we need to watch for are the "heavy metal" group. Iron, steel are not among those. The hobby we are in tends to promote hysteria and once written it is there forever but some looking around can show lots of reason to believe the normal metal is not a problem for most tanks. It is not at all uncommon to find things like bolts and screws in tanks. Also it is reasonably common to use galvanized steel tanks as outside ponds for both fish and plants. 
Some looking at the gallery on the forum may show some of those. I also use metal screws to hold my wood to the slate.


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## JonA (Mar 8, 2017)

PlantedRich said:


> As mentioned it is not really too common to find actual rust in rocks. One reason is that rust weathers pretty quick and as the rock has been out in nature for a few million years, it is likely to be gone. Far more common to find "rust colored" rocks which are actually other materials like reddish clay deposits.


Depends where you live. I grew up in Northern Minnesota where most of the iron in the US comes from. There are rusty rocks there. They have rust on the exposed surface and if you break them in half they are a dark charcoal color. Some places a compass won't work, and metal detectors are useless because they are constantly registering.


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## Malakian (Aug 23, 2014)

PlantedRich said:


> ...Iron, steel are not among those.



Just to nitpick. Steel can indeed contain heavy metals but not very often. Usually when you need some-kind of special attribute. The common "mixers" are chromium, vanadium, manganese and molybdenum. Steel is just a general term for a Iron-alloy with 50-99% iron and 0.1-2.5% carbon.


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## GrampsGrunge (Jun 18, 2012)

Our water source percolates through iron bearing sandstone and old weathered Andesite and other ancient lava. It's actually a boon because my tanks do well for Iron supplementation, as long as I can keep the pH below 7.0. What we don't have is decent amounts of other minerals like Calcium and Potassium, our water is really soft being rain water with a lot of tannins from the forest.


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## PlantedRich (Jul 21, 2010)

Malakian said:


> Just to nitpick. Steel can indeed contain heavy metals but not very often. Usually when you need some-kind of special attribute. The common "mixers" are chromium, vanadium, manganese and molybdenum. Steel is just a general term for a Iron-alloy with 50-99% iron and 0.1-2.5% carbon.


Quite right, in that odd things in small quantities can be found many places. Like radioactive particles in the porcelain items for a foreign ship?
But in general, metal is not really the big bugaboo that it is often painted to be. Rational thinking will show that almost all of our water does already have some iron or other metals in it. 
Iron ore is in the ground, in differing amounts all around the country. So are all the heavy metals we fear so much but they are mostly in small enough quantities that they are not a problem even though our water runs through them in the ground. Much more common is the metal that water picks up in our plumbing use. The pumps, pipes, vales and even our own faucets are made of brass, copper and various metals we often call iron or steel. 
So the question may be , what do we want to worry about? Do we sweat over using a rock that might look like rust, even though our water has already spent years and years in and around the stuff? In the mining areas like Minnesota, the water is stained rust colored due to the iron ore but then how many fish live in the lakes in the area? 
I think I remember folks going fishing in the Boundary Waters area and thinking the fishing was great.
Maybe iron doesn't really kill fish after all? 
If you are into raising the really fussy stuff, that is a different situation but one that you have chosen.

Dilution is the solution to pollution. Do a few water changes and enjoy!


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## Malakian (Aug 23, 2014)

I've been a oilfield service technician for close to eight years, so I see quite a few "uncommon" steel-types. So you might say I am overly interested in metals and alloys 

But in general, no such alloys are in daily use to the consumer/regular household. Just good old SS and high/low carbon Iron.


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