# what does chemical filtration really do?



## Aquarius Keeper (Sep 22, 2008)

There's so much talk about the nitrogen cycle and mechanical filtration is pretty intuitive - but I have to admit I still have a pretty vague idea of what those little bags of carbon are actually accomplishing.

To put it another way, what specifically would happen in an aquarium with biological and mechanical filtration, but no chemcal filtration?


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## Flashygrrl (Jan 18, 2008)

Um....generally around here we use it just to pull meds out of the water because it tends to strip some necessary stuff out of the water, especially if you're running a tank with plants. It can absorb some heavy metals and chlorine (think Brita) but not enough to actually replace water conditioners. I usually don't have it in my filters.


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## Tyyrlym (Jun 1, 2008)

It removes chemicals from the water. It's hard to be more exact about it than that. It's benefit is something that's not entirely agreed upon by many people. Personally I leave it in because I don't medicate and I have no plants. I just change it out monthly.

I am considering to going to one cartridge with carbon, the other without it but two filter pads instead.


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## Pasfur (Mar 29, 2008)

{sigh}

I am probably the biggest believer in chemical filtration on this site. You don't recognize the benefits unless you test Nitrate and hardness frequently.

Chemical filtration, especially activate carbon, removes organic waste directly from the water. These organic compounds have many negative effects on the overall system. For starters, they are metabolized by the biofilter, resulting in Nitrate buildup. Perhaps more important, the process of metabolizing these organics steals buffers from your buffer system, resulting in the need for more frequent water changes and a closer monitoring of pH and General Hardness. Finally, and not to be forgotten, organic compounds taint the water, reducing light penetration which is valuable in both marine reef systems and freshwater live plant tanks.

The only real negative to chemical filtration is the removal of trace elements which might be utilized by live plant or coral growth. Saltwater reef systems face this head on, by adding supplements into the system as needed. My live plant knowledge is limited, but I suspect a similar process could exist in a live plant setup with regular supplementation.

If you haven't noticed, I like carbon.-)


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## 1077 (Apr 16, 2008)

I am with Tyyrlym and Pasfur. I have seen no convincing evidence that using carbon is harmful to fish. In my opinion unless you have a planted aquarium or live rock in SW tank the benefits of carbon cannot be dismissed very easily. I pesonally use the carbon filters until they begin to fall apart. I simply take them out every couple weeks ,swish em around in old aquarium water that I take out and then stick em back in. When they begin to fall apart i replace them with new ones.


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## Little-Fizz (Aug 19, 2007)

I disagree, I find that carbon isn't very useful. I do have planted tanks though, but carbon if left to long in your tank can lead to hole in the head. Plus you have to buy new filter media every month, but if you cut the filter floss and empty the carbon you can reuse the media for wayyyyy longer. I'm all for recycling though. 

As for carbon being useful for removing waste from your tanks, its nothing compared to what a few live plants and a good 25-30% water change every week can do. 

IMO ditch the carbon and go for some live plants.


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## Tyyrlym (Jun 1, 2008)

I haven't heard or seen anything conclusive about HitH. Everything seems to be purely supposition and conjecture. It also all depends on having left your carbon in too long which is not a problem with carbon, its a problem with your maintenance procedures. Leave your mechanical filter in too long and it'll gunk up, kill your flow and your fish will die from ammonia poisoning. Doesn't mean there's anything wrong with mechanical filtration, just means you keep up on your maintenance.


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## Little-Fizz (Aug 19, 2007)

I wasn't implying that chemical filtration is bad, but that with regular, proper maintenance there is no need for it. 

And even if the hole in the head isn't for sure... Its really not worth the risk.

But obviously we all have our own views on this subject, just IMO ditch the carbon.


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## 1077 (Apr 16, 2008)

Little-Fizz said:


> I wasn't implying that chemical filtration is bad, but that with regular, proper maintenance there is no need for it.
> 
> And even if the hole in the head isn't for sure... Its really not worth the risk.
> 
> But obviously we all have our own views on this subject, just IMO ditch the carbon.


 With all due respect you DID suggest that carbon was bad. you stated that it would cause hole in the head disease when there is no evidence of that.


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## Pasfur (Mar 29, 2008)

Come on. Seriously. ANY filter used incorrectly is bad.

Replace your carbon on the proper schedule.


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## Little-Fizz (Aug 19, 2007)

Hahaha alright, I guess I did a little. But I was really just weighing the pros and cons.


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## 1077 (Apr 16, 2008)

I know you were.


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## iamntbatman (Jan 3, 2008)

I don't use carbon on any of my tanks. Sure, the conjecture relating to hole-in-the-head is simply that, but I still don't see that the risks outweigh the rewards.

Fresh activated carbon is *very* good at removing organics from your water. This means that any good organics in your water (i.e. compounds that could be used by your fish or plants for healthy growth) aren't free for use. Water changes help to replace some of these materials, but again if you have a high flow rate through a filter with fresh carbon, those added-back materials aren't going to last very long. If you're using liquid fertilizers, using activated carbon would be like flooring the gas and brake pedals at the same time. I also have a bit of blackwater going on in some of my tanks that would be impossible to achieve while using carbon.

So if my tanks are healthy and beautiful and my fish are happy and breeding, why would I spend the extra money on constantly replacing the carbon? Provided you're doing regular water changes (which are much less of a pain both cost and time wise for freshwater tanks than they are for saltwater) then the two benefits Pasfur talked about - nitrate buildup and hardness depletion - aren't real concerns. In fact, many freshwater fish (many new world cichlids, the tetras, barbs, loaches, etc) prefer softer water and would actually benefit from this buffer depletion effect, provided pH swings were prevented. pH itself is pretty easy to control in a freshwater tank since pH-raising additives like calcium aren't being dosed and tapwater pH tends to be fairly steady.

I guess I'm sort of rambling at this point. I recognize completely why these concerns would apply to a saltwater tank but I believe wholeheartedly that the use of activated carbon in freshwater systems is just a gimmick the industry has come up with in order to have hobbyists send them parts of their paycheck on a regular basis.


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## Pasfur (Mar 29, 2008)

iamntbatman said:


> I don't use carbon on any of my tanks. Sure, the conjecture relating to hole-in-the-head is simply that, but I still don't see that the risks outweigh the rewards.
> 
> Fresh activated carbon is *very* good at removing organics from your water. This means that any good organics in your water (i.e. compounds that could be used by your fish or plants for healthy growth) aren't free for use. Water changes help to replace some of these materials, but again if you have a high flow rate through a filter with fresh carbon, those added-back materials aren't going to last very long. If you're using liquid fertilizers, using activated carbon would be like flooring the gas and brake pedals at the same time. I also have a bit of blackwater going on in some of my tanks that would be impossible to achieve while using carbon.
> 
> So if my tanks are healthy and beautiful and my fish are happy and breeding, why would I spend the extra money on constantly replacing the carbon? Provided you're doing regular water changes (which are much less of a pain both cost and time wise for freshwater tanks than they are for saltwater) then the two benefits Pasfur talked about - nitrate buildup and hardness depletion - aren't real concerns. In fact, many freshwater fish (many new world cichlids, the tetras, barbs, loaches, etc) prefer softer water and would actually benefit from this buffer depletion effect, provided pH swings were prevented. pH itself is pretty easy to control in a freshwater tank since pH-raising additives like calcium aren't being dosed and tapwater pH tends to be fairly steady.


Very good arguments and worth further though.


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