# Is rust really dangerous?



## daniella3d (Mar 19, 2014)

I just came upon a thread for filling a petition to remove metal from aquarium decoration and a few people where actually putting the death of their betta on this. Some even mentionned that it was causing ammonia spike?

how?

I was just wondering because I have quite a few plants that have bits of rust. So far no trouble though with the fish.

Also I used to be a marine aquarist and we do put quite a bit of iron in our system to remove the phosphates. We even run it with a reactor to make sure the water goes through it. These particles are ferrous oxide, and when you rinse it off on first use the water become totally rusty. Some pople even forget to rinse it and their reef become rusty in color for a white with no ill effect.

So what's whith the rusty plants? is that really dangerous? any info stating facts on this? I would like to see if there is some, I would like to read it. So far I was under the impression that a bit of iron rusting in the water is quite harmless?


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## LittleBlueFishlets (Nov 10, 2012)

I can't speak about this from the perspective of the people writing the petition. Hopefully, they'll answer your questions regarding that. I also can't speak about this from experience, since I've never had this problem, or even looked into it.....

From a pure chemistry viewpoint, however, I can speculate on how the process could cause pH to rise. And as the pH increases, this could facilitate the conversion of ammonium to ammonia. 

If you're still reading (  ), here goes:

The corrosion of iron (rusting) requires both oxygen and water. The process can be accelerated by other factors (pH, presence of salts, etc). It's an electrochemical reaction, in which the metal conducts electricity.

Here are the two half-reactions that occur:
Cathode: O2 + 4H+ + 4e- --> 2H2O and/or O2 + 2H2O + 4e- --> 4 OH-
Anode:	Fe (s) --> Fe2+ + 2e- 

Since OH- is being produced at the cathode (and H+ is being used up), the pH would rise. This can then affect the relative ammonia/ammonium ion concentrations, "pushing" the equation towards ammonia:

NH4+ + OH- <--> *NH3* + H2O

Had enough yet? I can keep going.....  Again, this is pure speculation, based on some electrochemical principles. I have no idea whether this process would occur in a more complex system, such as an aquarium. (Mostly, I'm just procrastinating. Taxes are due tomorrow, and I've been really good about finding "stuff" to do so that I can avoid them!)


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## givemethatfish (Feb 10, 2014)

I will admit that I haven't studied chemistry in a number of years, but I cannot think of a way in which rust would have any affect on ammonia. Unless the fish were eating the rust, I can't see how it would really affect them unless there was a WHOLE lot on the water. 

However, I think your plants have diatoms or algae and not actual rust. Where would it come from unless you're sprinkling it in your tank?


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## TheTrojanBetta (Jul 4, 2013)

If the plants have metal wires in them, I would imagine there could be rust on them. But, I'm very careful not to have metal-wired plants and I know nothing about chemistry so I can't say for sure... I have heard horror stories of bettas getting impaled on metal wires that rusted and poked through a plant though, particularly certain leaf hammocks.


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## Hallyx (Jun 11, 2011)

Excellent explication, LiBlFi. That agrees with my understanding of the chemistry involved (although I['m not well-versed enough to have explained it myself). 

All red-blooded animals need a certain amount of iron to support hemoglobin. 

And, while I guess too much iron could be toxic to fish (it is to us), I think what little would ever build in an aquarium would not meet that level. Sounds to me like an over-reaction on the part of some overly-conscientious keepers.


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## daniella3d (Mar 19, 2014)

ok keep going, I am listening 

If order to transform ammonia in toxic form, it must first be present an in an uncycled tank. I understand that at higher PH the ammonia is more toxic, but in a normal tank there is no ammonia so this is not a problem. If the ammonia is present, then it could kill the fish wether there is rust or not.

right?



LittleBlueFishlets said:


> I can't speak about this from the perspective of the people writing the petition. Hopefully, they'll answer your questions regarding that. I also can't speak about this from experience, since I've never had this problem, or even looked into it.....
> 
> From a pure chemistry viewpoint, however, I can speculate on how the process could cause pH to rise. And as the pH increases, this could facilitate the conversion of ammonium to ammonia.
> 
> ...


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## LittleBlueFishlets (Nov 10, 2012)

Yes, there would need to be ammonium (NH4+) present in order for it to convert to NH3. However, many people on this forum don't have cycled tanks. They just do frequent water changes (hopefully).

Also, as the corrosion occurs, it removes H+ from the water and/or produces OH-. This would cause the pH to rise, and could be a potential issue if there is a lot of corrosion occurring in the tank. (Although, I agree with Hallyx that it's unlikely there would be enough iron undergoing corrosion in the tank to make a significant impact on pH. To go from a pH of 7.0 to 8.0 would require a ten-fold decrease in H+ ions.) And, as the pH rises, it would inhibit the corrosion process, which would slow it down.


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## LittleBlueFishlets (Nov 10, 2012)

Fun with numbers.... Some more calculations, just in case you're still reading.  (I had to start a new post, as I was over the editing time limit.)

Increasing the pH from, say, 7.0 to 8.0, would require a ten-fold decrease in H+ ions. 

In a 1L tank: 
(0.1 mols H+ / 1L) x (1 mol e-/1 mol H+) x (1 mol Fe/2 mols e-) x (55.85 g Fe / 1 mol Fe) = 2.79 g Fe required per L.

A common tank size is 2.5 gal (9.5 L). So 26.5 g of iron would need to rust completely in order to increase the pH by 1 unit.

An unverified Google search said that one pound of size "16d" nails contains 40 nails, which means that each nail weighs approximately 0.4 ounces (11 g). 

Assuming that a nail is 100% iron, to increase the pH of a 2.5 gal tank from 7.0 to 8.0, approximately 2.5 nails would need to rust completely. 

BTW, this only accounts for the partial oxidation of iron. We've taken it from Fe(s) to Fe2+. But to form rust, it would need to oxidize further to Fe3+. This means that in a 2.5 gal tank: 
(0.1 mols H+ /1L) x (1 mol e-/1 mol H+) x (1 mol Fe/3 mols e-) x (55.85 g Fe /1 mol Fe) x (9.5L /1 tank) x (1 nail /11 g) = 1.6 nails would need to rust completely. 

Either way, that's a lot of iron. If this was my tank, I'd have removed the nails long before they reached 100% corrosion.


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## daniella3d (Mar 19, 2014)

haha, thanks a lot for the math! I am not too good at it myself but it was a very interesting read!

This means that it is very unlikely that any little bits of rust on an artificial plant would have any impact on a fish or the ammonia level.

I guess it is easier for some people to put the blame of loosing their fish to ammonia on a rusty plant rather then taking the blame for what they did wrong (lack of proper maintenance) and killed their fish. Ammonia can rise so fast! Yesterday I tested one of my quarantine tank for ammonia and it was at .25 ppm, although I did a 50% water change in the previous evening.

Problem solved, I will not remove my plants just yet because they have a little bit of rust showing at some spots. 

thank you so much for your time on this!





LittleBlueFishlets said:


> Fun with numbers.... Some more calculations, just in case you're still reading.  (I had to start a new post, as I was over the editing time limit.)
> 
> Increasing the pH from, say, 7.0 to 8.0, would require a ten-fold decrease in H+ ions.
> 
> ...


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## LittleBlueFishlets (Nov 10, 2012)

No, I wouldn't think that a bit of rust would cause an ammonia spike. I also can't see how it would harm the fish. (Metal oxides, such as rust, are stable.) But that's based on a knowledge of chemistry. Aquariums have live organisms in them, so there may be other considerations. 

Unfortunately, fish get sick - and it's often very difficult to determine the cause. It could be environmental, bacterial, viral, parasitical, etc. The symptoms of a sick fish are sometimes vague and/or overlap.... Perhaps someone's fish became ill, and the person noticed a rusty ornament was present. They assumed a cause/effect relationship existed. And then someone else's fish became ill, and the first person said, "Do you have a rusty ornament?" So people started to notice rust in tanks where fish had died.

To determine if there's a true relationship between rust and dying fish, maybe we should ask people who have HEALTHY fish if they have rust in their tanks. Of course, this might lead to a different assumption forming, if enough people say, "I have rust in my tank, and my fish are healthy." 

(You were a marine aquarist, and there'd be a lot more corrosion occurring in salt-water environments than there'd be in fresh-water. So if there was a correlation between rust and fish health, I suspect you'd have heard about it previously.)

It sounds to me like you have a really good background in fishkeeping. So I'd offer this suggestion: "Keep doing what you've been doing."  If something starts to go awry in your tank(s), I think you'll be able to come up with a plan of action pretty quickly.


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## daniella3d (Mar 19, 2014)

Yes, I guess this is a different process but in saltwater we use a lot of granular ferric oxide so that bind with phosphates and remove it, but it will also remove other elements as well. After about a month the iron is removed and replaced by new. It's the only way to remove phosphates without doing a lot of water changes.

http://www.advancedaquarist.com/2012/2/chemistry

Also in saltwater GFO (granular ferric oxide) is not harmfull to any delicate live, not to fish, not to coral, not to invertebrate. On the other end, carbon filtration is said to cause ''hole in the head'' disease, but so many people still use carbon! it is far more risky than a bit of rust maybe? 





LittleBlueFishlets said:


> No, I wouldn't think that a bit of rust would cause an ammonia spike. I also can't see how it would harm the fish. (Metal oxides, such as rust, are stable.) But that's based on a knowledge of chemistry. Aquariums have live organisms in them, so there may be other considerations.
> 
> Unfortunately, fish get sick - and it's often very difficult to determine the cause. It could be environmental, bacterial, viral, parasitical, etc. The symptoms of a sick fish are sometimes vague and/or overlap.... Perhaps someone's fish became ill, and the person noticed a rusty ornament was present. They assumed a cause/effect relationship existed. And then someone else's fish became ill, and the first person said, "Do you have a rusty ornament?" So people started to notice rust in tanks where fish had died.
> 
> ...


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