I Think I Found Out Why 10 Fish Died On The Weekend

[Truck]

24oC?

 

[zelda_leonhart]

Well my hubby is a chemist and when I asked him if it was possible for the carbon filter to leech out toxins after its been left for too long he said YES. He didn't have time to explain fully (he's at work) but he said he'd explain it to me later so I can perhaps update the post tonight.

(As an aside the chemical equation written above is incorrect)

So apparently this IS possible and you should never keep a carbon filter in for longer than recommended.

 

[Spishkey]

ive had old carbon bits in my tank for over a year, never had a problem? i cant reach the bottom of the filter chamber to get the bag out so just left it in there?

 

[MHunt]

There is no cemical reaction in the adsorbtion (not absorbtion) of chemicals from the water. The physical makeup of the carbon means that chemical particles are trapped by it's surface area, however over time when the carbon becomes saturated with the chemicals we are trying to capture they can start to leech out again and in great enough concentration they will pollute the water.

In a properly cycled and stable tank there should be no chemicals produced by the tank that can't be dealt with by the bacteria in the filter. The only chemicals that need taking out are ones that we put in that can't be broken down like meds, and so the only time you really need to use carbon is after treating your tank for something and you want to remove the meds from the water.

That said, for 10 fish to die it points to some kind of poisoning, i would have thought that the buildup of chemicals from leeching carbon would be slow enough that it would take a long time to become apparent. Where's the tank situated? are there any air fresheners near the tank? Have any aerosol sprays been used near the tank?

 

[tom_os]

yes but not very much. and there is a very secure lid on the tank.

the tank has been there over 3 months and this is the first sign of a problem

 

[Truck]

Well my hubby is a chemist and when I asked him if it was possible for the carbon filter to leech out toxins after its been left for too long he said YES. He didn't have time to explain fully (he's at work) but he said he'd explain it to me later so I can perhaps update the post tonight.

(As an aside!!!!!! the chemical equation written above is incorrect)

So apparently this IS possible and you should never keep a carbon filter in for longer than recommended.

There is no cemical reaction in the adsorbtion (not absorbtion) of chemicals from the water. The physical makeup of the carbon means that chemical particles are trapped by it's surface area, however over time when the carbon becomes saturated with the chemicals we are trying to capture they can start to leech out again and in great enough concentration they will pollute the water.

In a properly cycled and stable tank there should be no chemicals produced by the tank that can't be dealt with by the bacteria in the filter. The only chemicals that need taking out are ones that we put in that can't be broken down like meds, and so the only time you really need to use carbon is after treating your tank for something and you want to remove the meds from the water.

That said, for 10 fish to die it points to some kind of poisoning, i would have thought that the buildup of chemicals from leeching carbon would be slow enough that it would take a long time to become apparent. Where's the tank situated? are there any air fresheners near the tank? Have any aerosol sprays been used near the tank?

THANK YOU!!!

 

[Bignose]

Carbon releaseing something it has absorbed is highly unlikely,in fact unless some other chemical got into your tank to cause a reaction that would release something eles from the carbon it wouldn't ever happen.
Jazzz's Cake analogy is correct.

This is just plain wrong.

There is a process used in the chemical industry known as pressure swing adsorption (http/en.wikipedia.org/wiki/Pressure_swing_adsorption) where at one temperature and pressure chemicals are adsorbed and the at another temperature and pressure it is releases. All adsorption processes are reversible at some point.

This is simply because everything is in chemical equilibrium. When you change the conditions, the equilibrium point may change, but everything is in equilibrium.

Carbon works by equilibrium in the following way: There is a balance between the amount of stuff adsorbed and the amount of stuff in the water. Now, for chemicals that carbon takes up, this can be shifted highly in the favor of the majority being adsorbed on the carbon.

Maybe it will be clearer with an example. Say there is 1000 mg of substance X in your water. Further say that the carbon equilibrium is 99% efficient at taking up substance X out of your water at the temperature you keep your tank at. That means, at equilibrium, 990 mg of substance X will be adsorbed on the carbon, and 10 mg will still be in the water.

Now, that 99% is a constant. Say after the carbon has reached equilibrium in the above example, you did a 50% water change. So, that will take 5 mg of substance X away (taken out with the water). That means that now there is a total of 995 mg of substance X available in the system. And, all systems will tend toward equilibrium, so the carbon will release some of the adsorbed substance X until the 99% equilibrium point is reached again. In this case, the carbon will release 4.95 mg of substance X off of it so that there will be 9.95 mg in the water, and 985.05 mg of substance X on the carbon.

This is exactly why carbon (and any other adsorbent like zeolite) can and will release chemicals. Nature always, always tends toward equilibrium, and it will move in that direction unless other additional forces act on the system.

 

[mistyash]

If conditions in the tank were favorable to the carbon adsorbing pollutants, what made that change. I don't like the argument about temperature, because clearly the temperature the tank is at is favorable to the carbon taking things in, not out, otherwise we wouldn't ever use carbon. sorry, I just didn't think that was a valid point, since the temperature isn't changing.

 

[MHunt]

If conditions in the tank were favorable to the carbon adsorbing pollutants, what made that change. I don't like the argument about temperature, because clearly the temperature the tank is at is favorable to the carbon taking things in, not out, otherwise we wouldn't ever use carbon. sorry, I just didn't think that was a valid point, since the temperature isn't changing.

As Bignose said, temperature isn't the only factor, diluting the chemicals in the water at a water change may change the equilibrium point for the chemicals that are being held in the carbon which may cause some to leech back out into the tank water.

 

[OldMan47]

A very important point about what Bignose said is that the carbon is not releasing anything that would cause an increase above what you have already had in the tank. In his example, the carbon effectively reduced the theoretical contaminant from 1000 down to 10 ppm. At that point the carbon became ineffective at removing that contaminant. After that, a water change did nothing to further reduce the chemical concentration because the carbon tended to maintain the same 10 ppm in the tank. This is the reason that carbon should be removed when it is "exhausted". The carbon in his example did not make the water quality degrade but it did make the water change ineffective at further reducing the chemical concentration. If that chemical was one that you were trying to get rid of, the carbon kept the water change from making the situation better but did not itself make the situation any worse. What this means is that when carbon has done its job, remove it or it will make other control methods less effective. It does not mean the carbon will release chemicals that poison the fish. Placing the blame for a new problem on old carbon is misplacing the blame. Old carbon will have trouble removing new contaminants but won't make the problem worse. You need to find the real problem that introduced something new into the tank.

 

[mistyash]

Thanks, OldMan47, that's what I was basically trying to say. Unless something changes, the Carbon's not making things worse.

 

[HalcyonDays]

I don't know much about this, but as interesting as it definitely is, I'm not sure it is of a great deal of use or comfort to you Tom?

If your LFS pointed to Carbon as the likely cause of your fish deaths, then you can either believe them or not believe them? If you believe this 'old' Carbon to be the primary cause then at least it is something you have learned and you will either:

A) Do without carbon filtration in the future, or
B) Remove Carbon when it gets 'old' and you percive it not to be doing its job efficiently anymore, in future.

But as Oldman47 and Mistyash appear to be saying, it would seem that something else went very wrong. Your tank may have become contaminated and the Carbon did nothing to help, but didn't cause the problem in the first instance.

What did cause the problem in the first instance (if your stats were good as you have stated) is another matter...

Mark.

 

[tom_os]

I don't know much about this, but as interesting as it definitely is, I'm not sure it is of a great deal of use or comfort to you Tom?

If your LFS pointed to Carbon as the likely cause of your fish deaths, then you can either believe them or not believe them? If you believe this 'old' Carbon to be the primary cause then at least it is something you have learned and you will either:

A) Do without carbon filtration in the future, or
B) Remove Carbon when it gets 'old' and you percive it not to be doing its job efficiently anymore, in future.

But as Oldman47 and Mistyash appear to be saying, it would seem that something else went very wrong. Your tank may have become contaminated and the Carbon did nothing to help, but didn't cause the problem in the first instance.

What did cause the problem in the first instance (if your stats were good as you have stated) is another matter...

Mark.

thanks, well it has been interesting. when the fish died i managed to save the cories and pleco because i put them in an empty tank i had. i did 2 80% water changes on the comtaminated tank during the last week and put in fresh carbon. yesterday i took this carbon out and threw it away. i then reintroduced the fish and i am pleased to say they are doing great.

so thanks for everyones help

 

[Socks]

Gusse I'm wrong,it has happened once or twice.

Either way it's been figured that it wasn't the carbon being in to long per say,but the changes that happened to make it possible for a release of junk.Right?
Under normal conditions it should never happen,because we aim to keep stable conditions in our tanks (most of us),and without something wacky happening or lack of maintenance the changes couldn't happen.

 

[Bignose]

If conditions in the tank were favorable to the carbon adsorbing pollutants, what made that change. I don't like the argument about temperature, because clearly the temperature the tank is at is favorable to the carbon taking things in, not out, otherwise we wouldn't ever use carbon. sorry, I just didn't think that was a valid point, since the temperature isn't changing.

I think you misunderstood my point about temperature. My argument about temperature was just to point that whenever something disturbs the equilibrium, that's when conditions change. A change in temperature will change the equilibrium point. The pressure swing adsorption process I linked to uses both temperature and pressure to change the equilibrium. Changes in the concentration will change the equilibrium point. Any change in the system will cause a change in equilibrium. That's my point, not that a change in temperature in this case caused anything.